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CHAPTER 3 INTRODUCTION TO HTML AND XHTML
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ORIGINS AND EVOLUTION OF HTML
2 ORIGINS AND EVOLUTION OF HTML Derived from SGML Original intent: General layout of documents that could be displayed by a wide variety of computers Recent versions: HTML 4.0 – 1997 Introduced many new features and deprecated many older features HTML A cleanup of 4.0 XHTML 1.0 Just 4.01 modified to fit the XML syntax
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WHAT IS AN HTML FILE? HTML stands for Hyper Text Markup Language
3 WHAT IS AN HTML FILE? HTML stands for Hyper Text Markup Language An HTML file is a text file containing small markup tags The markup tags tell the Web browser how to display the page An HTML file must have an ‘htm’ or ‘html’ file extension An HTML file can be created using a simple text editor , like….? HTM or HTML Extension?
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BASIC SYNTAX HTML elements are defined using HTML tags.
4 BASIC SYNTAX HTML elements are defined using HTML tags. HTML tags are surrounded by the two characters < and > , called angle brackets HTML tags normally come in pairs like <b> and </b> The first tag in a pair is the start tag, the second tag is the end tag The text between the start and end tags is the element content HTML tags are not case sensitive, <b> means the same as <B>
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BASIC SYNTAX (continued)
5 BASIC SYNTAX (continued) This is an HTML element: <b>This text is bold</b> What is the start tag, content of the HTML element and the end tag? Tags can have attributes Attributes can provide additional information about the HTML elements on your page. Example, <body bgcolor="red"> Attributes always come in name/value pairs like this: name="value". Quote Styles, "red" or 'red'? Comment form: <!-- … --> Browsers ignore comments, unrecognizable tags,line breaks, multiple spaces, and tabs
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HTML DOCUMENT STRUCTURE
6 HTML DOCUMENT STRUCTURE <html> <head> <title>Title of page</title> </head> <body> This is my first homepage. <b>This text is bold</b> </body> </html> The whole document must have <html> as its root A document consists of a head and a body or frameset The <title> tag is used to give the document a title, which is normally displayed in the browser’s window title bar (at the top of the display)
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BASIC TEXT FORMATTING Paragraph Elements W3C HTML Validation Service
7 BASIC TEXT FORMATTING Paragraph Elements The <p> tag breaks the current line and inserts a blank line The new line gets the beginning of the content of the paragraph W3C HTML Validation Service Line breaks The effect of the <br /> tag is the same as that of <p>, except for the blank line, No closing tag! Example of paragraphs and line breaks On the plains of hesitation <p> bleach the bones of countless millions <br /> who, at the dawn of victory <br /> sat down to wait, and waiting, died. What is the typical display of this text??
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BASIC TEXT FORMATTING Headings 8
Six sizes, 1 - 6, specified with <h1> to <h6> 1, 2, and 3 use font sizes that are larger than the default font size 4 uses the default size 5 and 6 use smaller font sizes
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BASIC TEXT FORMATTING Font Styles and Sizes (can be nested)
9 BASIC TEXT FORMATTING Font Styles and Sizes (can be nested) Boldface - <b> Italics - <i> Larger - <big> Smaller - <small> Monospace - <tt> Superscripts and subscripts Subscripts with <sub> Superscripts with <sup> Example: x<sub>2</sub><sup>3</sup> Display: x23 All of this font size and font style stuff can be done with style sheets, but these tags are not yet deprecated
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BASIC TEXT FORMATTING Character Entities Horizontal rules 10
There are some characters that HTML treats as special characters, so if you want one in a document, it must be coded The Most Common Character Entities: Horizontal rules <hr /> draws a line across the display, after a line break
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11 LINKS A link is specified with the href (hypertext reference) attribute of <a> (anchor) tag The content of <a> is the visual link in the document The syntax of creating an anchor: <a href="url">Text to be displayed</a> This anchor defines a link to W3Schools: <a href=" W3Schools!</a> How the line above will look like this in a browser?? Links can have images: <a href = "c210data.html" <img src = "smallplane.jpg" alt = "Small picture of an airplane " />>Info on C210 </a>
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LINKS The Target Attribute The Anchor Tag and the Name Attribute 12
With the target attribute, you can define where the linked document will be opened. <a href= target="_blank">Hi</a> The Anchor Tag and the Name Attribute The name attribute is used to create a named anchor. When using named anchors we can create links that can jump directly into a specific section on a page. The line below defines a named anchor: <a name="tips">Useful Tips Section</a> To link directly to the "tips" section, add a # sign and the name of the anchor to the end of a URL, like this: <a href=" Jump to the Useful Tips Section</a> A hyperlink to the Useful Tips Section from WITHIN the file "links.htm" will look like this: <a href="#tips">Jump to the Useful Tips Section</a>
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13 IMAGES Images are inserted into a document with the <img /> tag with the src attribute The <img> tag is empty, which means that it contains attributes only and it has no closing tag. src stands for "source". The value of the src attribute is the URL of the image you want to display on your page. The syntax of defining an image: <img src="url"> The Alt attribute is used to define an "alternate text" for an image. The value of the alt attribute is an author-defined text: <img src="boat.gif" alt="Big Boat"> In which cases, the ALT attribute will be useful??
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LISTS Unordered Lists Ordered Lists 14
The list items are marked with bullets (typically small black circles). An unordered list starts with the <ul> tag. Each list item starts with the <li> tag <ul> <li>Coffee</li> <li>Milk</li> </ul> Here is how it looks in a browser: Coffee Milk Ordered Lists The list items are marked with numbers. An ordered list starts with the <ol> tag. Each list item starts with the <li> tag. <ol> <li>Coffee</li> <li>Milk</li> </ol>
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TABLES A table is a matrix of cells, each possibly having content
15 TABLES A table is a matrix of cells, each possibly having content The cells can include almost any element A table is specified as the content of a <table> tag A border attribute in the <table> tag specifies a border between the cells Tables are given titles with the <caption> tag, which can immediately follow <table> Each row of a table is specified as the content of a <tr> tag The row headings are specified as the content of a <th> tag The contents of a data cell is specified as the content of a <td> tag
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16 TABLES <table border = "border"><caption> Fruit Juice Drinks </caption> <tr> <th> </th> <th> Apple </th> <th> Orange </th> <th> Screwdriver </th> </tr> <th> Breakfast </th> <td> 0 </td> <td> 1 </td> <th> Lunch </th> <th> Dinner </th> </table>
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TABLES A table can have two levels of column labels 17
If so, the colspan attribute must be set in the <th> tag to specify that the label must span some number of columns <tr> <th colspan = "3"> Fruit Juice Drinks </th> </tr> <th> Orange </th> <th> Apple </th> <th> Screwdriver </th>
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18 TABLES If the rows have labels and there is a spanning column label, the upper left corner must be made larger, using rowspan <table border = "border"> <caption> Fruit Juice Drinks and Meals </caption> <tr> <td rowspan = "2"> </td> <th colspan = "3"> Fruit Juice Drinks </th> </tr> <th> Apple </th> <th> Orange </th> <th> Screwdriver </th> ………… </table>
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19 TABLES The align attribute controls the horizontal placement of the contents in a table cell Values are left, right, and center align is an attribute of <tr>, <th>, and <td> elements The valign attribute controls the vertical placement of the contents of a table cell Values are top, bottom, and center valign is an attribute of <th> and <td> elements The cellspacing attribute of <table> is used to specify the distance between cells in a table The cellpadding attribute of <table> is used to specify the spacing between the content of a cell and the inner walls of the cell
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20 FRAMES Frames are rectangular sections of the display window, each of which can display a different document One common use of frames is to have a list of links in a left frame and use the right frame to display the destination document of the chosen link The <frameset> tag specifies the number of frames and their layout in the window <frameset> takes the place of <body>- Cannot have both! <frameset> must have either a rows attribute or a cols attribute, or both (usually the case) The possible values for rows and cols are numbers, percentages, and asterisks A number value specifies the row height in pixels - Not terribly useful! A percentage specifies the percentage of total window height for the row - Very useful!
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21 FRAMES An asterisk after some other specification gives the remainder of the height of the window Examples: <frameset rows = "150, 200, 300"> <frameset rows = "25%, 50%, 25%"> <frameset rows = "50%, 20%, *" > <frameset rows = "50%, 25%, 25%“ cols = "40%, *"> The <frame> tag specifies the content of a frame The first <frame> tag in a <frameset> specifies the content of the first frame, etc. Row-major order is used Frame content is specified with the src attribute Without a src attribute, the frame will be empty (such a frame CANNOT be filled later)
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22 FRAMES Scrollbars are implicitly included if needed (they are needed if the specified document will not fit) If a name attribute is included, the content of the frame can be changed later (by selection of a link in some other frame) <!-- frames.html An example to illustrate frames --> <html> <head> <title> Frames </title> </head> <frameset cols = "20%, *"> <frame src = "contents.html” /> <frame src = "fruits.html" name = "descriptions” /> </frameset> </html>
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23 FRAMES <!-- contents.html - The contents of the first frame of frames.html, which is the table of contents for the second frame --> <html> <head> <title> Table of Contents Frame </title> </head> <body> <h4> Fruits </h4> <ul> <li> <a href = "apples.html" target = "descriptions"> apples </a> <li> <a href = "bananas.html" bananas </a> <li> <a href = "oranges.html" oranges </a> </ul> </body> </html>
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24 FRAMES
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FRAMES Nested frames - to divide the screen in more interesting ways
25 FRAMES Nested frames - to divide the screen in more interesting ways <frameset cols = "40%, *"> <frameset rows = "50%, *"> <frame src = "frame1.html" /> <frame src = "frame2.html" /> </frameset> <frameset rows = "20%, 35%, *"> <frame src = "frame3.html" /> <frame src = "frame4.html" /> <frame src = "frame5.html" />
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26 FRAMES
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27 FORMS A form is the usual way information is gotten from a browser to a server HTML has tags to create a collection of objects that implement this information gathering The objects are called widgets (e.g., radio buttons and checkboxes) When the Submit button of a form is clicked, the form’s values are sent to the server All of the widgets, or components of a form are defined in the content of a <form> tag The only required attribute of <form> is action, which specifies the URL of the application that is to be called when the Submit button is clicked action = If the form has no action, the value of action is the empty string
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28 FORMS The method attribute of <form> specifies one of the two possible techniques of transferring the form data to the server, get and post. What are differences between these two methods? Widgets Many are created with the <input> tag- The type attribute of <input> specifies the kind of widget being created Text Creates a horizontal box for text input Default size is 20; it can be changed with the size attribute If more characters are entered than will fit, the box is scrolled (shifted) left If you don’t want to allow the user to type more characters than will fit, set maxlength, which causes excess input to be ignored <input type = "text" name = "Phone" size = "12" >
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FORMS Checkboxes - to collect multiple choice input 29
Every checkbox requires a value attribute, which is the widget’s value in the form data when the checkbox is ‘checked’ A checkbox that is not ‘checked’ contributes no value to the query string By default, no checkbox is initially ‘checked’ To initialize a checkbox to ‘checked’, the checked attribute must be set to "checked"
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FORMS 30 Grocery Checklist <form action = ""> <p>
<input type = "checkbox" name = "groceries" value = "milk" checked = "checked"> Milk <br/> value = "bread"> Bread value= "eggs"> Eggs </p> </form>
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31 FORMS Radio Buttons - collections of checkboxes in which only one button can be ‘checked’ at a time Every button in a radio button group MUST have the same name If no button in a radio button group is ‘pressed’, the browser often ‘presses’ the first one Age Category <form action = ""> <p> <input type = "radio" name = "age" value = "under20" checked = "checked"> 0-19 <br/> value = "20-35"> 20-35 value = "36-50"> 36-50 value = "over50"> Over 50 </p> </form>
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FORMS Menus - created with <select> tags 32
There are two kinds of menus, those that behave like checkboxes and those that behave like radio buttons (the default) Menus that behave like checkboxes are specified by including the multiple attribute, which must be set to "multiple“ The name attribute of <select> is required The size attribute of <select> can be included to specify the number of menu items to be displayed (the default is 1) If size is set to > 1 or if multiple is specified, the menu is displayed as a pop-up menu Each item of a menu is specified with an <option> tag, whose pure text content (no tags) is the value of the item An <option> tag can include the selected attribute, which when assigned "selected" specifies that the item is pre-selected
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FORMS 33 Grocery Menu - milk, bread, eggs, cheese
<form action = ""> <p> With size = 1 (the default) <select name = "groceries"> <option> milk </option> <option> bread </option> <option> eggs </option> <option> cheese </option> </select> </p> </form>
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34 FORMS After clicking the menu After changing the size to 2
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FORMS Text areas - created with <textarea> 35
Usually include the rows and cols attributes to specify the size of the text area Default text can be included as the content of <textarea> Scrolling is implicit if the area is overfilled Please provide your employment aspirations <form action = ""> <p> <textarea name = "aspirations" rows = "3” cols = "40"> (Be brief and concise) </textarea> </p> </form>
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FORMS Reset and Submit buttons --> SHOW a browser display of a form
36 FORMS Reset and Submit buttons Both are created with <input> <input type = "reset" value = "Reset Form"> <input type = "submit” value = "Submit Form"> Submit has two actions: Encode the data of the form Request that the server execute the server-resident program specified as the value of the action attribute of <form> A Submit button is required in every form --> SHOW a browser display of a form
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EXtensible HyperText Markup Language (XHTML)
37 EXtensible HyperText Markup Language (XHTML)
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WHAT IS XHTML? XHTML stands for EXtensible HyperText Markup Language
38 WHAT IS XHTML? XHTML stands for EXtensible HyperText Markup Language XHTML is aimed to replace HTML XHTML is almost identical to HTML 4.01 XHTML is a stricter and cleaner version of HTML XHTML is HTML defined as an XML application XHTML 1.0 became an official W3C Recommendation January 26, 2000. All new browsers support XHTML
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39 WHY XHTML? The following HTML code will work fine if you view it in a browser, even if it does not follow the HTML rules: <html> <head> <title>This is bad HTML</title> <body> <h1>Bad HTML </body> XML is a markup language where everything has to be marked up correctly, which results in "well-formed" documents. XML was designed to describe data and HTML was designed to display data. XHTML is a combination of HTML and XML Today's market consists of different browser technologies Browsers run internet on computers, mobile phones and handhelds.
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40 WHY XHTML? XHTML pages can be read by all XML enabled devices AND while waiting for the rest of the world to upgrade to XML supported browsers, XHTML gives you the opportunity to write "well-formed" documents now, that work in all browsers and that are backward browser compatible !!!
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XHTML VS HTML XHTML elements must be properly nested
41 XHTML VS HTML XHTML elements must be properly nested <b><i>This text is bold and italic</i></b> XHTML documents must be well-formed <html> <head> ... </head> <body> ... </body> </html> Tag names must be in lowercase <BODY><P>This is a paragraph</P></BODY> [WRONG!!] <body><p>This is a paragraph</p></body> [CORRECT!!] All XHTML elements must be closed <p>This is a paragraph</p> Empty elements must either have an end tag or the start tag must end with />, any EXAMPLE???
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XHTML SYNTAX Some More XHTML Syntax Rules:
42 XHTML SYNTAX Some More XHTML Syntax Rules: Attribute names must be in lower case Attribute values must be quoted Attribute minimization is forbidden The id attribute replaces the name attribute The XHTML DTD defines mandatory elements All XHTML documents must have a DOCTYPE declaration. The html, head and body elements must be present, and the title must be present inside the head element. The DOCTYPE declaration is not a part of the XHTML document itself. It is not an XHTML element, and it should not have a closing tag.
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XHTML DTD The basic document structure is:
43 XHTML DTD The basic document structure is: <!DOCTYPE ...> <html> <head> <title>... </title> </head> <body> ... </body> </html> The DOCTYPE declaration defines the document type: <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" " DTD is used by SGML applications, such as HTML, to specify rules that apply to the markup of documents of a particular type, including a set of element and entity declarations.
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44 XHTML DTD XHTML is specified in an SGML document type definition or 'DTD'. An XHTML DTD describes in precise, computer-readable language the allowed syntax and grammar of XHTML markup. There are currently 3 XHTML document types: STRICT Use this when you want really clean markup, free of presentational clutter. Use this together with Cascading Style Sheets.
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XHTML DTD 45 TRANSITIONAL
Use this when you need to take advantage of HTML's presentational features and when you want to support browsers that don't understand Cascading Style Sheets FRAMESET Use this when you want to use HTML Frames to partition the browser window into two or more frames.
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46 XHTML VALIDATION An XHTML document is validated against a Document Type Definition. Before an XHTML file can be properly validated, a correct DTD must be added as the first line of the file. Test Your XHTML With The W3C Validator
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