Web application Must Support all the Browsers

This is not a problem with your backend C# stuff, it's entirely a problem with your CSS styling. There's a wealth of information on supporting older browsers out there - just do some searching on IE6 compatibility, for example.

As for supporting all the browsers, unless you want to stick with no styling and just straight HTML, it's impossible. Period. Seriously, there's probably someone in a basement somewhere using LYNX.

I wish you luck - supporting older browsers takes an enormous amount of work. I would suggest that you ask your "other users" to upgrade their browsers, if possible.

I don't know enough to tell you any more. Perhaps with some more information, I could give you a more specific answer.

Like everyone else said, you have to take each browser into account in your styling (CSS) and layout. Every brwoser interprets the HTML and CSS standards a bit differently.

There's a lot of work involved and how much you do depends on which browsers and versions you want to support.

Exactly what you do to support these browsers depends entirely on your page layout, styling and requirements. Noone is going to be able to tell you exactly what to do in a forum environment.

As for a PERFECT solution to this problem, there's no such thing!

Welcome to the joys of web development!

As a suggestion;

Dont restrict your self to computers. Now a days people browse website from their mobile phone, ipdas, i-pods, tablets, etc .

As a general practice, i always develop UI for websites which are center aligned to the screen. and then a similar image which repeat itself on both the sides to fill the empty space.

You can find few of such tempaltes on Template Monster