font-size:20px; assigns a length of 20 pixels to font-size.
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"> <head><title>CSS Syntax</title> <meta http-equiv="Content-type" content="text/html; charset=utf-8" /> <style><!- body { font-size:20px; } </style> </head> <body> <p>CSS syntax is <span style="font-style:italic;">EASY!</span></p> </body> </html>