Maybe this is a post for me, maybe it is a post for my mom the math professor… either way, all I know is that when I specify “font-size: 12px; line-height: 150%;” , Internet Explorer 7 puts a little bit more space in between lines than Firefox and Safari do. Now quick math says that 150% of 12 = 12 x 1.5 = 18 . And if I say “font-size: 12px; line-height: 18px;” , everyone behaves the same, correct spacing across all browsers. Learn to multiply, IE7. Please, send me a postcard when you graduate from 2nd Grade. Thanks.