Google Hides its Text: Why Can't We?
Are hidden-text penalties a hoax?
There are more articles about why hidden text is bad for SEO than the number of tacos I've consumed over my life-time. And I freaking love tacos.
<h1><a id=logo href="http://www.google.com/webhp?hl=en" title="Go to Google Home">Google<img width=167 height=222 src="/images/srpr/nav_logo13.png" alt=""></a></h1>
I thought to myself: Hey, isn't that what people do when they're replacing text with an image by moving the text off screen so they can trick search engines?
Well....#logo img{border:none;position:absolute;left:-0px;top:-41px}Google's image logo is positioned over the h1 text. Remove the image tag and you see a tiny Google link.

Hiding text or links in your content can cause your site to be perceived as untrustworthy since it presents information to search engines differently than to visitors. Text (such as excessive keywords) can be hidden in several ways, including: * Using white text on a white background * Including text behind an image * Using CSS to hide text * Setting the font size to 0Hmph. The trickery doesn't end there.
<h2 class=hd>Search Results</h2>Examining class hide reveals
.hd{position:absolute;width:1px;height:1px;top:-1000em;overflow:hidden}If you do a browser-search for the phrase "Search Results", the results will be found, but you can't see the text on the screen.