When specifying parameters in CSS, you can use many different units.

• em (ems, the height of the element's font)
• ex (x-height, the height of the letter "x")
• px (pixels, relative to the canvas resolution)
• cm (centimeters; 1cm=10mm)
• mm (millimeters)
• pt (points; 1pt=1/72in)
• pc (picas; 1pc=12pt)