Well, its going to be CSS or JS and CSS combined somewhere down the line.
- Rip out 50% of your CSS file.... still have the problem?...
- Get rid of another 50%.... still have the problem?
- get rid of 50%.... problem is gone?
- get rid of all the rest and put back the section that had the issue.... still have the issue? ...
- get rid of 50%.
When you have isolated the CSS causing the issue, remove and rewrite it in a way that does not cause the issue.