Getting quick answers to grammar-related questions can be a challenge. Here’s a great free online resource called Common Errors in English Usage by Paul Brians. Brians is an Emeritus Professor of English at Washington State University- http://www.wsu.edu/~brians/errors/errors.html
Many grammar guides offer lengthy convoluted descriptions of grammar rules. I especially like this one because of its practical nature. If you have a question about, say, using semicolons, use the search engine or click the letter “S” and you’ll find a concise explanation of how and when to use semicolons.
This is a helpful link for times when grammar questions arise. Near the bottom of the home page are links to additional online grammar resources recommended by the author.