I would advise strongly against placing invisible text on your page to get higher rankings in Google. This is one of the big no-nos that can get your pulled off of Google completely. They consider putting invisible words on your site dishonest since only content on the page should be there for their spider to search.
I agree... don't do it. It might work for a while, but it's not fair. Someone can contact Google and tell them about your unfair competition, and I bet that Google will soon find a way to see these cheaters. If they find you, your site will get banned and no more hits for you from Google.
