Ouch. Is every single item in that CSS relevant to the problem, so if you delete any one thing the problem disappears?
If so, you're on your own :)
The usual starting point for CSS issues is to get rid of the whole CSS and then add items one by one until the display breaks. Don't even think about the rest of the page; just work on the part that isn't behaving as intended. For example, if you have a problem with header alignment, it is very unlikely that the color of the footer text will make any difference.