It was hard to restrict this to just ten things, but here are ten things related to writing on the Web that are causing me to break out in hives when people don't manage to follow basic writing guidelines that they should have learned in high school. Please, proofread before you post, and yes, that includes titles too. Yes, I know, everyone makes mistakes, and heaven knows I do, but we should at least try for basic literacy.

1. It's is a contraction for it is. Possessive pronouns (its) don't have apostrophes.
2. Titles of long works (movies, television series titles, plays, books, and albums) are italicized. In the U.S. use double quotation marks for short works, like short poems, short stories, and article titles.
3. Learn the differences between accept and except, stationary and stationery, complementary and complimentary, lose and loose, and principal and principle.
4. Web site is capitalized; it's derived from the proper noun World Wide Web. Note that you cite a Web site.
5. Either curse or be courteous; masked expletives and obscenities are amateurish and cowardly. Be a grown-up and curse for real—or be adept and refrain from cursing. English has a centuries-old tradition of increasing vocabulary by taking the best of other languages. You don't get "nice points" for using biatch instead of bitch; you're a writer; surely you can do better than minced oaths.
6. Learn the differences between a hyphen, an em-dash and an en-dash. That means don't use - for —.
7. Link to your sources and to related online content.
8. Don't create links that open a new browser window; it's exceedingly poor practice in terms of user experience and usability since it disables the function of the Back button. Jacob Nielsen compares it to a vacuum cleaner salesperson who begins his pitch by dumping an ash tray on your carpet. Let users decide how and where they want links to open.
9. Have something intelligent, interesting and thoughtful to say. Please don't waste readers' time by offering little more than a summary and paraphrase of your source.
10. Leave room for comments to provide an alternate viewpoint, or to take the conversation in a new direction.