can any body suggest me some websites name where i can host my web app. freely?

I think you will be very lucky to find a free MS based webhost, but as a Java one exists (myjavaserver) you might be lucky. If you are developing a FB app (or can build a FB app into your project) and don't mind using Mono + MySQL rather than MS based products (does Mono include the web stuff?) then you might be able to use Joyents free FB offer. They appear to be giving away VPSs for a year (before charging large amounts of money), so if you can install mono etc onto it you will be away. http://joyent.com/developers/facebook

The only site i can think of is Bravenet, they offer alot to do with webpages but i am not sure that is what you are looking for but it is worth a look, other than that all i can think of is one of the many free blog sites...Good luck.