Today ajax is being a common part in most large website and
application.user loves the way everything done without page
refresh and website's with ajax implemented is getting higher
popularity.in the following i showed how to use ajax in asp.net
web page.you can use in php too -

following way a DataTable with data can be used to
populate gridview control in asp.net.following codes get files list
from a file path and adds in DataTable then sets that
DataTable as a DataSource of the GridView grdDirList.

asp.net routing is easy to use for rewriting any url.

if you have a url like wwww.aspdotnetsite.com/Projects?user=username.
but if you want to have it in short name for marketing or for anything
you want like this is the resulting url -
wwww.aspdotnetsite.com/Projects/username

It's a good idea to identify the errors at run time to detect
and handle it. .Net framework has built in mechanism for that.
these exceptions occurs because of user,logic and system errors.

following codes shows how to use GridView control.Its a
simple example.

in app main file -

using System;
using System.Collections.Generic;
using System.Linq;
using System.Windows.Forms;