If you have some of the following as a part of your website design, you can be sure that visitors to your site find it annoying.
1. Background music - it is only for an internet radio or a site that sells CDs.
2. Huge font size - the kind that shouts at you. Keep in mind that no one likes being shouted at.
3. Small font size - the exact opposite of being shouted at i.e. huge font size. If, you wish to be heard, a normal tone at a reasonable volume is required.
4. Layers that overlap are 'too much in your face' message screaming. Subtle persuasion is far better than employing sheer 'brute force'.
5. Popup windows - even while these are blocked by add on tools, certain website designs continue to employ them. Why not place your important messages in a central part of your web design rather than trying to get them across with the help of irritating pop-ups.