1. Autoplay video.
Let your visitors make the decision whether they want to watch or not. The videos can also slow down your site.
2. Pages that load slowly.
Cut the Flash presentations and the splash pages with “enter” buttons; they slow people down. People want information, not commercials. The exception to this is if you’re a filmmaker, film editor, or web video producer. In that case, you’ll need Flash to show off your skills. Just make it a voluntary click (not an auto play), and put it on a clips page (rather than the home page).
3. Sign in forms.
Don’t make it harder for visitors to find information. If you want to keep paid content separate, or need a user login for accounts, that’s fine, but don’t try to capture information from everyone who visits. You’ll drive people away.
4. Hard to find contact information.
If it looks as if you’re hiding, your trust level will go down. Put your address, email, phone number, etc. where people can find it easily.
5. Poor usability.
If visitors have trouble finding what they want, and broken site search, they’ll leave in frustration.