ERRATA (err-ah-tah; plural noun)
Errors in printing or writing, especially such errors noted in a list of corrections and bound into a book. [Latin errātum, from neuter past participle of errāre, to stray.]
Old hands have learned this the hard way--this TECHknitting QUICKtip is for newer knitters, and was inspired by a novice knitter I overheard in my LYS last winter--asking the workers why the pattern she'd bought a few weeks earlier wasn't working. The idea that it wasn't her fault--that the pattern could be wrong--clearly shocked her.
THENIn the old days, publishers would send out "errata notices," little strips of paper that your LYS was supposed to paste or tape into a booklet to correct the errors the publisher found out about only after the booklet was published. Similarly, when you bought a pattern book, a flurry of little errata slips often fell out as you opened the book for the first time. The publishers quaintly believed that since the error was theirs, they ought to fix it.
NOWWith the advent of the web, publishers and designers have put the onus on YOU to check their websites to see if errata have been published. It would behoove you to do that--there are pretty much no publishers immune, and magazine patterns seem particularly prone to being full of errors. Not to mention yarn company patterns.
Bottom line: check the publisher's web site for pattern errata BEFORE you cast on. Heck, check the whole web--bloggers often find problems...before publishers do...