Have you fixed it yet?

If not, in your browser "tools" options you should see "manage add-ons" then "toolbars and extensions".
Look for names that are unknown to you (not Microsoft, Adobe, Oracle etc) and that do not match any software you knowingly installed. This might leave 1-2 culprits. Do a google search on the remaining extensions to see what they are. You will quickly find out if they are junk that can be disabled and the cause of your highlighted/underlined links. With extensions since you can disable/enable without deleting you could just try disabling one at a time too.

I assumed you are running Windows with Internet Explorer. I have to do this on my in-laws computer every time I visit. As well as remove about 15 programs and browser toolbars they have no idea how they got, lol.