Getting screen width and height

Using 2005 express edition asp.net.  Need to get the width and height of the screen the user currently has who is viewing the site.  Is there any easy way to do this?  Do anyone have an example of code that will do it?  My problem is that I developed my website on my laptop and when it is viewed on a larger screen the form does not fill out the whole screen.

 

Thanks in advance for your assistance
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