[jQuery] Beginners question: how to set width on an element

[john6630]

I want to read the body width when a page loads and set an element's
width to the same width. The reason I want to do this is that the page
is generated programmatically. Alternatively I can have the program
set the width value to a constant but in any case, I believe I need to
do this when the page is loaded versus a CSS file that is not created
by the form generator.

Here is what I have tried:

        <style type="text/css">
                body
                        {
                                margin: 0 auto;
                                width: 430px;
                        }
        </style>

    <script type="text/javascript" src="~/JavaScript/
jquery-1.3.2.min.js"></script>
    <script type="text/javascript">
      $(document).ready(function(){
      $("ul.AspNet-Menu").width() = $("body").width();
      });
    </script>

Note: my program that creates the page sets the body width. So I could
replace the code with
      $("ul.AspNet-Menu").width() = "430px";

TIA,
John