Without knowing what went wrong (maybe she updated the theme, overwriting all your custom code?), I think it could be fixed quickly if you do this:
- change
width: 700px;
to width:100%
in #content
- add
width: 700px;
and float: left;
to .post
That should fix it for the single pages. But, not knowing much more about the site, I’m not sure what impact it’ll have on the rest of the pages, so check it properly everywhere.
Or, if you want these fixes only to apply to single pages, adding this piece of code might be easiest:
.single #content {width:100%;}
.single .post {width: 700px; float:left;}