So there are common punctuation errors that crop up again and again in web interfaces, and do much to confuse users. Here are the key problems.

  1. Finishing punctuation on headings
  2. Weird bullets
  3. Using dashes instead of commas (or parentheses, or colons)
  4. The greengrocer’s apostrophe
  5. Ampersands in text

read the whole thing @ 5 Common Punctuation Problems to Avoid – SitePoint.

Why is this important? Because every element of your site speaks to the user on some level… and the negatives add up.