here's some css that you can use as an exmaple of what css to use and what changes what by inserting them into your extra.css template. bare in mind change the colours to suit your preference.
If memory recalls, I had to fix the css on the nature calls membercard after a xf update the devs making some changes to it. I doubt you messed anything up as several members on my site had similar issues which they alerted me to which prompted me to make the necessary fixes.