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nope, nothing has changed in the page itself, we submitted a couple of articles and exchanged some links and the ranking went up to 10. After a week the ranking went back to 20... I don't think I can't disclose the website, but what makes you think that the one you mentioned was the website in question? it sounds  bit dodge...

Ideally it should not be used on a logo because as others have said here it is a bit black hat and an alt would be preferable. but it is often used as part of css menu systems with no ill effect. http://www.htmldog.com/articles/suckerfish/dropdowns/ Is a perfect example of a widely used menu system that is build around text shunted off  the page until it is the focus.