what i do for finding these issues is to use Fire Bug in Fire Fox.
In fire bug, my strategy is to go to the CSS Tab, and from the drop down list, select the main sites CSS File.
I then select the first selector name and hit the delete key, then the tab key, this removes that first selector, and tabs to the next one. I keep deleting and tabbing through the style sheet and checking the page layout to see if the problem i am trying to target still exists or not.
once I delete a selector and tab to the next one, and the problem goes away, i make not of the selector name. now i know to investigate the selector before it.
Refresh the page and go back into the css file to locate the problem selector, and this time, disable individual styles in that selector to narrow the issue down.
First step is destructive troubleshooting, keep removing classes and pair away the layout till you find the culprit. keep removing bits of the haystack till you find the needle.
