Try the following:
Often you are not seeing your changes because the browser has cached the stylesheet. "F5" refresh the browser.
- Check the Stylesheet Syntax
A simple syntax error like a missed bracket or an unfinished comment tan disable huge portions of a stylesheet. In the make a custom look screen we have a link to a stylesheet checker. the link will automatically send the CSS fromt he currnet look. Use this link and look over the messages carefully. If it does not say "this validates as CSS" then you have a problem that should be fixed and which might account for your problem. Also look at the final CSS it reports to see if parts of your declarations have been skipped.
- Save the web page locally
One basic trick that comes in handy is to save the web page locally, and then view the local copy in your browser while you edit out one class at a time to see which is governing the setting you want to change.