I just discovered another reason a sidebar will drop to the bottom of the page.
Options/Reading set your posts showing to 4 or less.
BACKGROUND: I had my blog working fine with this setting at 999.
However, after some work was done on the blog that didn't work out well, the sidebar dropped to the bottom of my homepage and some, but not all category pages. The rest of the pages, i.e. other categories, all monthly archives, and all permalinks to individual posts were fine.
Steve Duncan helped me this morning, and after looking at a variety of places for a way to fix this, we tried changing the number of posts showing. For the home page, we could set it at 26 and the sidebar would reappear. However, in order to fix it on the other pages, we had to go to no more than 4 showing.
I have no idea why and figure someone else will want to know about this.
I'm using DaisyRaeGemini Theme on WordPress 2.x
The blog is at:
Steve Duncan's blog is at:
<http://www.lornitropia.net/> and I'll be checking his blog to find other tips.