If I am lucky, I know just enough about typography to write this article. If the way the article is set appeals to you, you can probably thank your browser, or luck, I am no type expert by any means. I wonder at the artists who create fonts—fontographers and those who know how to use them well—typographers. This post is about how to use certain typographical characters correctly in XHTML documents.
em and en are units of typographical measurement. An em is the size of the letter M. Since type sizes may vary the size of an em is relative to the size of the type. (An em inside of an <h1></h1> is larger than an em in <h2></h2>)