Are you aware of the penalties for using hidden text? This out dated technique is Spam. Never try to add keywords or text to a page, in the same color font as the exact background color, thus making text appear hidden.
Spam Alert: Don’t EVER use hidden text, hidden links or hidden “anything” on a page unless you want to risk setting off some warning flags and risk getting in trouble.
Content Rich Pages
Create a content rich, informational site which is loaded with quality articles, tips, free advice, and tutorials, and keep your options to buy a product very subtle.
Call to Action
Make sure your top scoring high performance pages include a call to action.
You simply can’t beat the old ‘hot-linkers’ that used to fill their pages with links off site and hide them by using the exact background colour on the href. That and keywords. I believe that google now has a very specific ability to check for this and removes indexes for sites doing just that
Good quality content is always the route to take, its surprising to see that some people still persist with spammy attempts at SEO. Take a look at my article on the customer street forum to see my views on the subject http://www.customer-street-forum.com/viewtopic.php?f=7&t=13