I am having the same issue.
I have changed in style.css
#index { width: 240px; background: #fff; /* line-height: 1.3em; */ }
#exhibit { margin-left: 240px; }
Nothing changes on the site, and when I look at the page source info, it looks like something is overridding my changes:
Basically, where is the following css coming from - listed after the links to css
a:link { color: #0000ff; }
a:visited { color: #404040; }
a:hover { color: #0000ff; }
#index { width: 215px; }
#exhibit { margin-left: 215px; }
#index, #exhibit { font-size: 12px; }
#index, #exhibit { line-height: 18px; }
.container { padding-top: 36px; }
.container { padding-left: 36px; }
#index, #exhibit { color: #000; }
#index, #exhibit { font-family: Arial, Verdana, sans-serif; }
#index ul.section span.section_title, #index ul.section span.section_title a, #index ul.section span.subsection_title, #index ul.section span.subsection_title a { font-size: 12px; }
#img-container { width: 5619px; }
#img-container .text { float: left; width: 627px; }
#img-container .text p, #img-container .textor p { width: 592px; }
#img-container .text2 p { width: auto; }
#img-container .picture { float: left; }
#img-container .captioning { height: 50px; text-align: left; overflow: visible; }
#img-container .captioning .title { margin-top: 3px; text-align: left; }