Common WebSite Mistakes
1. Do Not use Animated GIFs
They are out-of-date and distracting to users.
2. Always set body background-color
Not everyone uses white in his browser as the default background color.
3. Check for Cross-Browser Compatible
Not all browsers are created equal, and not all of them interpret CSS and other languages on the same way. Like it or not, you will need to make your website compatible with the most used browsers on the market, else you will lose visitors over the long term.
4. Do Not add Audio Background
It’s annoying for 99.99% of the visitors, but If you must play an audio file let the user start it.
5. Do Not Start Videos Automatically
Same as 4. but for videos 
6. Do Not use Horizontal Scroll
Do you like to scroll horizontally !?
7. Do Not Type All Text in CAPS
8. Avoid “intros”
Do not force the user to watch or read something before he can access to the real content. This is plain annoying, and he will stay only if what you have to offer is really unique.
9. Avoid Long Pages
If the visitor needs to scroll down forever in order to read your content he will probably just skip it altogether. If that is the case with your site make it shorter and improve the navigation structure.
10. Always Add Enough White Space
White space is an important principle of design missing from the page layouts of many novices. White space is nothing. White space is the absence of text and graphics. It breaks up text and graphics. It
provides visual breathing room for the eye. Add white space to make a page less cramped, confusing, or overwhelming.
