if ur creating windows application mdi forms is very common. is this also possible with web application?

like typical mdi (multiple document interface) win apps.. u can drag the windows inside, minimize, maximize...etc.

if possible, can someone pls tell me how to do it?

Well, you must make them in javascript, flash or have a java applet that implement it.

Web applications are not desktop applications, they behave a lot differently, and the whole architecture is different.
But if you want to try it that way, try to get documentation and tutorials on AJAX.
The problem is, taht in windows dev. world, you have high level libraries to do that.
Not much in the web world. There are many javascript frameworks out there, but nothing as advanced as what you might look for.

Honestly, I wish you good luck (you'll need it if you really want to do this)...