Aoccrdrnig to rseerach at Cmabridge Uinervtisy, it deosn't mttaer waht oredr the ltteers in a wrod are in, the olny iprmoatnt tihng is taht the frist and lsat lteter be at the rghit pclae.
The rset can be a tatol mses and you can sltil raed it wouthit a porbelm.
Tihs is bcuseae the huamn mnid deos not raed ervey lteter by istlef, but itesand rades wrods as a wlohe. Amzanig, waht?
(Tahkns to Feirdns of the Cahepl Hlil Pluibc Lrbiray Nweetlster.)
UPDATE: See comments at Eric's link, which include a reference to an interesting post at Languagehat.