putting hiden links text on a site is a big no no in seo, try it and see how quickly google and the other big search engines ban your site. quoted from google:
'Quality Guidelines - Specific recommendations:
* Avoid hidden text or hidden links.
* Don't employ cloaking or sneaky redirects.
* Don't send automated queries to Google.
* Don't load pages with irrelevant words.
* Don't create multiple pages, subdomains, or domains with substantially duplicate content.
* Avoid "doorway" pages created just for search engines, or other "cookie cutter" approaches such as affiliate programs with little or no original content. '
http://www.google.com/webmasters/guidelines.html