Hyperlink CSS

I use the Paid Membership Pro plug-in. The hyperlinks are not showing as hyperlinks, which is super confusing. I added this CSS below, which corrected it, but then caused all my hyperlinks to show that way:

a{
background: 0 0;
text-decoration: underline;

}

The downsize, is that as this is clearly a common class, other site links show that way that didn’t previously (and that I liked as they were), in particular my mobile menu – all my mobile menu items are underlined.

How can I fix this? Can I create a custom CSS class for the mobile menu or the PMS plug-in so one is not affecting the other? I would also like to change the color of the PMS hyperlinks, but clearly can’t do it without other items being affected (when I did it, the collapsed mobile menu changed to that color, too).

http://www.yogoonthego.com