I'm in the process of redesigning this one website that has a good mix of internal and external links in the body of just about every page. A lot of the visitors are middle-age and many have asked to make external links open in a new window automatically. So i was thinking of making the external links look slightly different from internal ones, to give the visitor a clue of where they're going. Maybe use a dashed underline instead of a solid one, coupled with "External website: " in the link's title attribute.

Any thoughts on this? Any usability studies on this subject? Or is there a better way? Thanks.