Underlining is a common tool for emphasizing the text or marking a link. Basically, it is just a line that is situated under some text segment.
If speaking about the usage of underscores, one cannot forget about the underlined hyperlink in blue color, that is the most common and identifiable feature in the user’s online experience.
It is not always justified to use the underlining in combination with a color as a hyperlink emphasizing tool, but this design is the most recognizable one. It allows the user to easily navigate through the text and indicates the links you have already visited by changing the color of a typeface.
However, there could be cases when designers would want to make the hyperlink decoration more creative. Here are some alternatives for underlining links:
Underlining is a nice tool to indicate the key text or mark a link. One last hint here is once you decide where to implement it, do not use it for the other words in the text block.