In your source code, you need to find the ul element with the class of "ul1" and modify the width. This will also affect the top navigation since you called that ul1 as well.
What I would do is edit the file that has the side boxes and give that ul a name tag, something like leftNav or something like that. Then eyou will need to add that new id to the styleshee file. you should leave the class attribute in the ul tag so it still has all the styling of the other ul's.
HTML Code:
<ul class="ul1" id="leftNav">
<!-- add this to the stylesheet -->
ul#leftNav {width:300px;}
To find where the HTML is, use the Developer Tool Kit.
In the Admin goto Tools->Developers Too Kit to search for this string using the lookup in all files field at the bottom.
HTML Code:
<!--content col1 cell1 -->
You should get a list of files that have that string in them, there you can add the id tag to the ul.