The solution I posted is what is necessary to control that text. You don't need to make #mainWrapper 100% or fluid width, but you do need to separate it from the rest of the list.
Code:
#headerWrapper, #contentMainWrapper, #logoWrapper, #cartBoxListWrapper, #ezPageBoxList, #cartBoxListWrapper ul, #ezPageBoxList ul, #mainWrapper, #popupAdditionalImage, #popupImage {
width: 900px;
margin-left: auto;
margin-right: auto;
padding: 0em;
}
Separate into two declarations and style as required:
Code:
#mainWrapper {
width: 900px;
margin-left: auto;
margin-right: auto;
padding: 0em;
}
#headerWrapper, #contentMainWrapper, #logoWrapper, #cartBoxListWrapper, #ezPageBoxList, #cartBoxListWrapper ul, #ezPageBoxList ul, #popupAdditionalImage, #popupImage {
width: 100%;
margin-left: auto;
margin-right: auto;
padding: 0em;
}
You also have not completely fixed the #mainWrapper premature closure yet, so this CSS will make the page body expand. Rather than try to hide the symptom by calling it 900px, find and remove the extra </div> tag, probably in tpl_header.php. Until you do that, you are asking for random unexplained problems.