Website for Common Errors in English

English professor Paul Brians of Washington State University has a great website describing a large number of "Common Errors in English" in very readable (and frequently funny) prose. He describes his intention: "Here we’re concerned only with deviations from the standard use of English as judged by sophisticated users such as professional writers, editors, teachers, and literate executives and personnel officers. The aim of this site is to help you avoid low
grades, lost employment opportunities, lost business, and titters of amusement at the way you write or speak." He also notes that his site "is dedicated to errors in usage. This is not a site dealing with grammar in general."

There are literally hundreds of entries (e.g., reign/rein, if I was/if I were, premier/premiere), arranged alphabetically.

source: MoLIB