Site archetecture question

they usually use mod rewrite to rewrite the URL... So you're right. they don't have different pages.

If you're familiar w/ Joomla!, it does something similar when it changes a link using mod rewrite from

http://tbare.com/index.php?option=com_content&view=article&id=4&Itemid=4

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to

http://tbare.com/portfolio

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One page that calls the users profile from the db is the correct answer.

In apache web server on linux this is done using a special file called .htaccess that sits in a directory and consists of rules for sending the browser to a different page that is displayed. A very simple example of a .htaccess file would be:

Options +FollowSymlinks
RewriteEngine On
RewriteRule page_that_does_not_exist.html page_that_does_exist.html

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- in this example the page that the web browser displays is not the one that the user has typed into the address bar of the web browser. Create the page_that_does_not_exist.html and you can call it from the other url in the file - which remains displayed in the address bar.

.htaccess files use regular expressions too:

RewriteRule /user/(\w+)/ homepage.php?user=$1

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In the example above the parentheses grab are used to capture a match and store it in $1 - fairly standard regular expression behaviour - which can then be passed as a GET variable to the script that is called. If you make multiple matches they go into $1,$2,$3 etc and you pick them up in your script as usual - in the example above you'd use $_GET['user']

http://corz.org/serv/tricks/htaccess2.php - the first link from searching "htaccess mod rewrite" in google - looks like it covers it all in more detail.

so with mod rewrite does google still index every user's page?

great information thanks.

Any URL can be indexed by Google.  The URL itself is not very important, except as a human-centric mnemonic.  It's easier to remember something like http://twitter.com/LandonBaseball but the computers do not really care about the URL.  Google cares about the content of the pages, most particularly about the title and h1 tags as well as the meta description.  Google also cares about how many other pages link to any given page, and what the other page links contain in the text of the anchor tag.

This is a good book that teaches the basic design of data base backed web sites.  General purpose scripts create the HTML for pages.  The exact content of any page is determined from the contents of an underlying data model.
http://www.sitepoint.com/books/phpmysql4/