you may have Genieo installed
see
http://www.genieo.com/faq/#q20
Note that, if Genieo is installed, using the recommendations that Genieo themselves provide on that page will not remove it. They cannot be trusted, and their uninstaller is known not to remove everything. Proper Genieo removal instructions can be found in my Adware Removal Guide.
I don't believe this is a Genieo problem, though. Genieo usually just hijacks the search engine. It doesn't cause the random underlined words that cause ads to pop up. That's going to be caused by some other adware, probably also described in my Adware Removal Guide.
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