Troubleshooting Your Blogs CSS and Sidebars

Just spent an hour futzing with CSS code and PHP for the Coachamatic re-launch. There was some little piece of code that was making the sidebar appear below all the content on the homepage but correctly on all the other pages. I realized how to fix this much faster:
Set the number of posts on the homepage to 1.
Rebuild and reload.
Is the CSS still broken? Set the number of posts on the homepage to 2.
Rebuild and reload.
Rinse and repeat.
Finally it turned out the third post was throwing off the HTML. As usual it was one tiny small DIV tag that broke the whole design.