I don't have any hard data but my observations and conversations with several folks seem to indicate that visitors like to see the underline.

It easily identifies the links at a glance and for whatever reason many come to expect to a link be underlined.

I don't know of any surveys that have been done, but if I were to hazzard a guess, I'll bet if you asked a large group how they can tell what's a link, the majority would say it's underlined.

Dave

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