Javascript is one of the most important language for webdevelopement. We need to build the interactive websites. For the desktop application Messagebox are very important thing for building interactive websites. But from server side (asp.net) we can not display messageboxes and other things. But with the help of java script we can display the alert(Messagebox) messages on our websites.I have found a great link on this. Here is the link:
http://www.devnewz.com/devnewz-3-20061129JavaScriptAlertShowmessagefromASPNETCodebehind.html