Web Design Tutorial: Technical Do's and Don'ts for Every Web Designer

Don'ts:

1- Web positioning:
Don't center everything on your website pages.
Think about it for while, why printing design layout is always from left to right, not centered. Take an example all books pages layout is from left to right, imagine if you read a book with a center layout, it will be so hard to read and follow this way.
Finally it's up to you, but it's easier to read without a centered layout.

2- Marquee tag:
Don't use scrolling 'marquee' tag.
What is Marquee tag?? A normal HTML tag (that only works in Internet Explorer), allows you to create a quote like horizontal scrolling display of whatever text and words you put in-between the tags.Some of web designers like to use a marquee, but most web site visitors and surfers don't like to see it at all. Scrolling marquees make your page look cheap and take away from the rest of the page.
Be smart and avoid what your web visitor don't like.

3-Background Music:
Don't use background music on your web pages.
Background music is good for some web pages like MTV channel web site, this can work with them. But for most websites this is just a very bad idea simply for some reasons, for example file sizes for this music files are pretty heavy, so it take a long time to load for every web site visitor, in most cases it's not worth to wait for it.I know some web designer like to have a nice music files in web sites, if you have to do it so keep the choice to the surfer, by making it an option surfer can take off and on.

4-Java Scripts:
Don't rely on JavaScript to work on your pages.
About 20% of the internet users can't run JavaScript! that basically means that you can't use JavaScript for key features of your website. But it doesn't mean you forget it and don't use java at all, but if you use it be safe an try to have some alternative for your script in case your surfer can't run java scripts.