(This article is supported by Adobe.) An underline is a horizontal line immediately below a portion of text. In our everyday experience, we underline to emphasize key sections of text, sometimes drawing an underline by hand below printed text. But underlines have their own place in the world of digital design. In fact, underlined text has become one of the most common, most recognizable features of our online experience. When we see an underlined word or sentence on a web page, we immediately assume it’s a link.