Web Searching

How does a search engine work? It does NOT search the Web (when you make a query) It contains a database with info on numerous Web sites  When you do a search it looks through the database to find pages

Steps in Web Searching You type a string into the search box instituting a query. The search engine parses the string for key words The search engine looks through its database The search engine arranges the likely pages in order of relevance according to its algorithm The search engine builds a new Web page with the results and returns it to your browser.

How Does a Search Engine Determine the Contents of a Web Site URL (uniform/universal resource locator)- the address of the Web page Title of the page – it shows up in the title bar of the browser. Note recent browsers seem to have done away with the title bar (Chrome/IE9/Firefox6) so the title doesn’t show up anymore but the page still has a title. Metatags are tags in the header of a page that give info about the page. Text within the page

Spiders Search engines use programs called spiders to crawl the web examining various web pages and saving the information that they find in the database. 24/7/365 Pages are revisited to see if they’ve changed. Important pages are revisited regularly (amazon.com). Unimportant pages are revisited less regularly (cs.uofs.edu/~sidbury)

Determining Relevance Algorithms are used to rank pages. They are proprietary and trade secrets. So google’s algorithm and yahoo’s algorithms are different. The algorithms are the main difference between different search engines. Today most search engines are adding features to try and gain popularity from the market leader.

Determining Relevance (continued) Page Rank  How many other pages have links to this page Click Popularity  How often is this page chosen in similar searches Stickiness  How long does the user stay on the page after it’s clicked Sponsorship  Does the page pay the search engine to list it.  Sponsorship is common but typically is also labeled.

Why Don’t Search Engines Just Search The Web SPEED.

How Can Google Search Billions of Pages in Only a Few Seconds The pages are indexed.

Why do Porn Sites Show Up in Lots of Searches Lots of people search for Porn even when they claim that they are not. Pornographers try to trick search engines  Misleading metatags  The search engines are becoming more sophisticated so porn is less common in searches.

How Can You Increase the Visibility of Your Web Site Add metatags Give the page a meaningful Title Give the page a meaningful Name Use meaningful words at the beginning of the text of the page Use Error 404 tricks  Tricky names