Akemi Iwaya is a devoted Mozilla Firefox user who enjoys working with multiple browsers and occasionally dabbling with Linux. She also loves reading fantasy and sci-fi stories as well as playing "old school" role-playing games. You can visit her on Twitter and Google+.
The SPF, or Sun Protection Factor, of sunscreen is representative of the amount of UV radiation the sunscreen blocks; a sunscreen with an SPF rating of 30 will allow 1/30th of the UV radiation to reach the skin (blocking 29/30ths, when applied properly, from reaching the skin). Conventional sunscreens are designed to block UVB radiation while broad-spectrum sunscreens are designed to protect against both UVB and UVA radiation.