Why are underlines so underused?

Bold, italics, and underline, are not arbitrary variations of emphasis, but help us with the difficult job of quickly absorbing ever more information. If a text deploys them thoughtfully, each of them fulfills a distinct role and catches our attention only under a certain semantic condition while it is almost transparent in all other circumstances.

• Bold, for instance, is the macro markup that serves as eye-catcher and helps with long-distance jumps into a paragraph when we are skimming text.
• Italic, on the other hand, is the micro markup that takes effect only within a narrow, local context, when our eyes have reached the respective text portion. Therefore, it is ideal for marking up text that is just somehow different: pronounced with stress, or being a term that will be explained, or a verbatim title or a quotation or a source name, or an antonymy.

And underline? Well, it could indicate all kinds of relationships or links, and in the early days of hypertext every link was underlined (and blue). Since then, we got considerably accustomed to thinking of some kind of “link” when we see some underlined words. And this is not limited to hyperlinks:

• also, acronym expansions or glossary-like explanations may be linked behind underlined markup (often with a special context-help cursor and sometimes with dotted underscore);
• when we work through a paper text, we underline noteworthy spots where we will later jump into the text again, i. e., a sort of link anchor as well;
• in visuo-spatial overviews of short text snippets (e. g. presentation titles of a conference, see #66, or bibliographic entries), we indicate the relationships of two snippets by connecting two text-boxes, and we can markup the most significant words with a bold eye-catcher. But if there is an additional relationship involving a second term in each text box, we can indicate these logical link endpoints by underlines, distinguishing the second, cross-reference link from the main concept mapping structure.

So the underline would be the ideal third partner of bold and italic.

But on more and more hypertext pages, the underlined hyperlinks have disappeared and have been replaced by colored links with or without glowing effects or other sorts of animation or visual gimmicks, because layouters and designers feel that their customers dislike mere underlines.

So why is underline so unpopular? Perhaps the underconscious reason is that it is the markup of teachers who, in our youth, marked calculus errors with a red pen, or of Word that today marks spelling or grammar errors with red and green underlines.