1. Font Size
Never force your visitors to read on your website. If they feel it is a struggle to read for more than 2 minutes, the font size is too small. The best bet is to read yourself. Choose a decent font size. It should not be too big as well.
2. Spelling/Grammar
Getting your visitors to guess what is the word is a turn off. Spelling and grammar can be easily corrected by writing your article on a Word program before you post it on your website.
Spelling and grammar are detected while you type and it can be corrected immediately. You might not be an English speaking writer but in order to thrive online, that is a language skill that you have to learn.
3. Too many graphics
Having a few graphics on your website is nice. But you must also consider the size of the graphic. I have seen website posting a very nice picture but it took more than 10 seconds to fully load that single picture. Can you imagine if you have 10 of such graphics on your website? Therefore always chose GIF over JPEG format for graphic since the file size of GIF will be smaller.
4. Background music
Although we are seeing fewer sites with background music but that does not mean it is not a problem to address. Background music is good if it is smoothing and blends into the theme of the website.
Unfortunately not everybody shares your kind of music and I would rather you err on the safe side by not using any at all. This is my personal opinion but if you think it is necessary for your business, I won't stop you.
5. Pop-up Advertisement
Pop-up advertisement is an effective selling tool. However I have seen pop-up advertisement that won't go away! It is good to get your pop-up advertisement being shown once to your visitors. Pop-up advertisement that won't go away is portraying to your visitors that you are hard selling them. This is definitely a turn off.
Last but not least, ensure you have a simple to understand navigation menu. All pages must be accessible within 3 clicks from the main page is a well adopted practice. Embedding your product pages too deep and you will be kissing your sales goodbye!