How to expand container divs to 100% when decreasing browser window?

[gauchomatt]

I have a liquid site which expands perfectly when the browser window is larger than the actual content. However, when I decrease the browser window size to a point that it's smaller horizontally than the content, my background div's and their images start to decrease horizontally.

I think it has something to do with my #main div as well as my #wrap div's. They are the ones decreasing horizontally and eliminating everything in their path except for images!

Here is my css for my main framework:

html, body { height: 100%; background-color: #d9d9d9; font-family: "HelveticaNeue", "Helvetica Neue", Helvetica, Arial, sans-serif; text-shadow: rgba(255, 255, 255, 0.8) 0px 1px 0px; }
 
#wrap { width: 100%; min-height: 100%;}
#header { background: #000 url('../images/head_bg.png') repeat-x; height:66px; }
#subhead { background: #000 url('../images/subhead_bg.png') repeat-x; height:202px; }
#main {background: #d9d9d9 url('../images/body_bg.png') repeat-x; min-height: 542px; overflow:auto; padding-bottom: 124px; /* must be same height as the footer */ clear:both; }
 
.container { width: 960px; margin: 0px auto; padding: 0px; border: 1px solid red; }
.sidebar { float: left; padding: 0px; width: 200px; border: 1px solid red; }
.content { float: right; padding: 0px; width: 730px; border: 1px solid red; }
 
#footer { position: relative; height: 124px; z-index: 20; margin-top: -124px; /* negative value of footer height */ clear:both; } 
#social { background: #000 url('../images/social_bg.png') repeat-x; height: 63px; z-index: 20; }
#bottom { background: #000 url('../images/bottom_bg.png') repeat-x; height: 61px; z-index: 20; }
 
#body_content { margin: 30px 0px 0px 0px; font-size:13px;  }

I have included a red border just for debugging purposes. I have found this same issue on some other sites as well. If you go to http://www.healthypayout.com (this is on a Mac) just make the browser window smaller horizontally, like pretty small, then you should have a scroll bar. Scroll over and you will see that the background images there are doing the same thing mine are.

If you need me to post my HTML here I can do so. Please help! Thank you all again. I have included two screenshots of what it does on my end in the .zip file.

Best,
Matt