@raveenasenJun 25.2013 — #Hidden text means showing something different to search engine and some showing something different to users on your site. Hidden text and invisible links are a technique which violates Google quality Guideline so we can't use them on our website.
@MultimasteryJun 25.2013 — #You can use it IF you want to risk you site getting banned very quickly by Google (and maybe other search engines, but other engines are not as strict as Google so you might be able to get away with it). If you want to try these stunts, just test them methods on a site you don't really care about and see what happens!
@Steve_SmithJun 28.2013 — #Google treat this type of hidden link or text as spam also known as clocking in terms of SEO.Admin of the site use this for crawler so that user can't see this hidden text or file but crawler crawl this hidden things.