Border around page

I have added borders to my ZenCart install. I originally used tables but have converted to divs to make them easier to manage. I have noticed that when a wide image pushes the right column over it goes over the border. How can I make the border expand with the cart?

http://liquorkicker.com

CSS:

.Bsize{
overflow:auto;
}
.Bstyle {
	position:relative;
	width:auto ;
	display:block;
	float:none;
	text-align:center;
	border-width: thick;
	border-color: inherit;
	border-style: solid;
}
.WrapperSize{
	width:900px;
}
.R {
	border-color: red;
}
.O {
	border-color: #FF9900;
}
.Y {
	border-color: yellow;
}
.G {
	border-color: lime;
}
.B {
	border-color: blue;
}
.P {
	border-color: purple;
}

PHP in tpl_main_page.php

<div id="mainWrapper" align="center">

<?php //Begin Border ?>

<div class="R Bstyle">
<div class="O Bstyle">
<div class="Y Bstyle">
<div class="G Bstyle">
<div class="B Bstyle">
<div class="P Bstyle">
<div>
<?php // End Border ?>

There are seven /div tags right before the mainwrapper /div

Remove width:900px; from #mainWrapper. If you use a fixed size it wont expand with the content. Thats why its called fixed size.

The divs still dont expand. When i used tables it expanded. I was hoping to use divs so it would be easier to manage.