Frequently Asked Question

Underline on the web typically means that something is clickable.
People click underlined words all the time, and if those words don't go anywhere, then they are less likely to click on other things that are underlined and clickable.

http://www.christophermerrill.com/blog/avoid-underlining-for-emphasis-on-websites/

http://practicaltypography.com/underlining.html