It's an oldie, but a goodie:)

Aoccdrnig to a rscheearch at an Elingsh uinervtisy, it deosn't mttaer in waht oredr the ltteers in a wrod are, the olny iprmoetnt tihng is that frist and lsat ltteer is at the rghit pclae. The rset can be a toatl mses and you can sitll raed it wouthit porbelm. Tihs is bcuseae we do not raed ervey lteter by it slef but the wrod as a wlohe.

But just to bring it up to date, I found this page which sets out to debunk the theory, but part way down provides a link to this letter which suggests there is at least some basis to it.

Notable in that letter is a statement that "This reminds me of my PhD at Nottingham University (1976), which showed that randomising letters in the middle of words had little or no effect on the ability of skilled readers to understand the text. Indeed one rapid reader noticed only four or five errors in an A4 page of muddled text."

Which tends to suggest that people who read faster, are generally quite happy to skip over spelling errors and typos. This has always been one of my excuses as I tend to derive meaning from entire sentences at time--with the sometimes obvious effect that I derive the wrong meaning if the construction of the sentence doesn't fit the patterns I'm expecting.

Whatever else, it made for an interesting read.