Saylor.org's English Composition/Grammar Capsule: Common Offenses
Perfect use of grammar is never easy in the English language. The English language prides itself on its versatility and adaptability. Unlike other languages, there is no governing body that officially sets the rules of English grammar. Although there are certainly conventions that if deviated from will make your writing seem amateurish. The good thing is that many people make the same mistakes. Habitually so. In this sense, it's easy to anticipate some of these common offenses by knowing how to identify them.