Think about the last time you left a website. Was it amateurish, cramped, overly busy or confusing – you couldn't work out where to go or what to do? Three seconds later you're out of there to find a business that's a better match for you.
Now think about some sites you really like. They're probably professional, clean, easy to navigate, with just one purpose for each page - they might look a bit like this one ;)
Too many websites - even by so-called designers - lack a clear visual flow and the understandable calls-to-action needed to get visitors to stay on your site long enough to find out what you're about, become clients and to give you their hard earned money.