I can think about some things that are always annoying: Wait for a person that always arrives late to meetings; that my computer comes up to an error before saving the job I've been working on for a long period of time; spam emails.
Even though, there's one very worse than those mentioned and it's an outdated website. Let's say I get a flyer of a company with a product or service that I interest. The first thing I do is write down the website and throw out the flyer (why put away more papers?), when I go to the site to know more about the company, just there start the problems.
Web design is complicated and dynamic. It combines different areas of knowledge that affects heavily how its target market sees the information given or make them want what you are offering. If you want the store to look excellent and have good conversion rates, the design plays an important role on this matter. Take note that this applies to both visual and simple to use (easy to browse, easy to search, easy to find, and easy to buy).
Before starting the list, remember that when building your ecommerce website your focus should be to MEET THE USERS' NEEDS, how simple is to find what they are looking for, fast loading, and a hassle free checkout is the ultimate goal of your store.
Instead of "showing off" what nowadays a browser can do, the passion of your webmaster should be directed to user friendly usability and good functionality of the shopping cart.
When you are looking to open your online store there are 2 available options. You could hire a design company and have them build you a site from scratch with shopping cart and all the bells and whistles, or…you could go with the much more attractive option of implementing a ready-to-go ecommerce solution, which you can adapt to your particular needs.
So, there you are with an excellent PSD design on your hands. Problem is, you need it converted into a Zen Cart custom design theme/template so you can conjure up a great website. The next step is to hire an experienced Zen Cart coder to get you on your way.