Avoid Hidden linksare the number of pages that link to one of your pages has a direct effect on how high your page appears in the search results (and that page's PR). As with hiding text, hiding links will also result in a ban or PR penalty.
Example of Hidden Links:
You put 200 Links That has a Anchor tag of "Make Money Online" that links to your Main Page and the color of the links are like the Background color of the site. So People wont See the Links but the GoogleBot will see it. And if google recognize your Hiden Links, that's the Time you will be penalize having a hidden links. Your PR Will Go Down and thats bad for a website.
See Also this post:
Avoid Hidden Text