As radiant_luv said, set the a: and maybe also a:hover in the css style sheet. Note that you may want to change the colour or something to make it obvious that it is a hyperlink - I'm not sure if Google penalises for "hidden links"?????
Why would they? I'm not saying they don't--I don't know what their rules are. But if you make a link hidden, it's not very useful, but doesn't detract from the otherwise usefulness of a site. So why would Google penalize them?