Animations, for example, are neurologically very distracting. Clearly label navigation links and use them consistently across the site. Provide directions where needed. Be a strong critic. Proofread Spelling and grammar matter.
Email is viewed as informal and no one seems to mind a few mistakes.
The web is not viewed this way. Something as simple and seemingly insignificant as misspelled words can cause you to lose credibility. Ask permission before borrowing graphics if you are not sure that they are in the public domain. Make sure all of your links work. Do a periodic evaluation of your site.