» The EMs have it: Proportional Media Queries FTW! Cloud Four Blog
“As I zoom in, that is, make the text larger in my browser, I’m no longer at a 14pt/16px baseline. 100%/1em in my world is now a different number, maybe 18pt, maybe 32px. Pixel-defined content holders no longer have comfortable amounts of words per line. Pixel-defined content holders that float might wrap awkwardly as the content in them swells.”