If there is one thing that can really hurt the success of your website, it's a bad website. Your design is of utmost importance, and if you cannot design well yourself then you should consider learning how to design well, hiring someone to design it for you, or buy a template from one of the many websites that sell them. If you want to do it yourself and don't have that good of skills then concentrate on keeping things simple, don't use bright colors, don't use much colors at all. Don't make it fancy, keep it simple and useable like a newspaper.
You may also think you design well when you really don't, in this aspect I'm not talking about HTML, HTML is arbitrary, I'm talking about designing. Knowing which colors go with which colors is not a skill everyone is born with, some people insist on putting bright blue right next to bright green. Additionally if you make your own graphics then you need to use a program that has anti-aliasing, otherwise your graphics will look pixilated and rough. Trust me, nothing makes a website look unprofessional more than a pixilated graphic.
The best thing you can do is decide which competitor of yours has the most professional looking site, and try to make your site as professional or even more professional. You don't have to do it on your first try, most website go through numerous redesigns, especially at first, but keep it in mind as a goal.