1. Splash Page
A splash page is the landing page of your site where it has a flash animation or just text that says “Enter”. A simple google search will show you tons of articles about why you shouldn’t have a splash page. There are two main reasons why a splash page sucks, it annoys customers and it is bad SEO.
Why does it annoy customers?
It’s basically another step users have to go through to get to the website they actually want to go to. They don’t want to watch your intro every time they go to your site. If you annoy a user enough they will just leave your site.
Why is it bad SEO?
Your landing page will probably have your highest page rank so having little content like text that says enter or an intro video will do little to get you hits from search engines.
Here is some more info
2. Header is to big
There is a term called “above the fold” which they use in the newspaper industry. It refers to the location of an important news story or a visually appealing photograph on the upper half of the front page of a newspaper. Most papers are delivered and displayed to customers folded up, meaning that only the top half of the front page is visible. Thus, an item that is “above the fold” may be one that the editors feel will entice people to buy the paper.
In web design we use a similar term called above the scroll. This refers to all the information the user can see without scrolling down. You want to use this area for your important content. When you have a huge header it makes the user scroll down every page to get to the content they are looking for. Use your space wisely and make sure your important content is above the scroll.
3. Product pictures are too small.
There are a lot of e-commerce systems out there and default themes for shops that make the product pics so small. If you are selling a shirt the images are more important than your description and should take up most of the space on the product page. Make your product pics big!
There are tons of problems I see with typography on the web but I am just going to comment on readability. Your text must be easy to read if you want someone to read it. One problem I see a lot is the text color doesn’t have enough contrast with the background. By the way the most readable text is black text on a white background. I have left many sites that have white text on a black background because it hurt my eyes after a while. If you only have a couple lines of text its not a big deal.
Another readability issue I see is there are too many characters on a line. According to a classic rule of Web typography, 55 to 75 is an optimal number of characters per line. Research done on smashing magazine showed that the average on websites is 88.74 characters per line (maximum). Having too many characters makes the user forget what line they are one when they go to the next line of type. If you have a 900px website and your content goes all the way across the 900px this text is going to be hard to read. Have a sidebar or break up your text into 2 columns.
There are tons more typography rules for the web in this article.
5. Music auto playing on site
Don’t do it! I have left so many websites and never returned because I couldn’t figure out where to turn off the music. Don’t annoy the customer and make them listen to something they don’t want to. If you want music make it so the user has to click the play button.