Many have found that the fewer clicks required, the better. In other words, the easier you make it to buy from you, the more likely people will. A large percentage of surfers dislike them. They can be confusing and awkward for users. It's tricky to get the HTML just right.
Search engines have problems indexing past the home page.
Of course, there are many other techniques and strategies for boosting web site profits, but this basic primer will help you avoid some of the most common response killers.