The $300 Million (Web Form) Button

Example from book
Web Forms Design

The $300 Million Button:
"It's hard to imagine a (user registration) form that could be simpler:
two fields, two buttons, and one link.
Yet, it turns out this form was preventing customers from purchasing products
from a major e-commerce site, to the tune of $300,000,000 a year.
What was even worse: the designers of the site had no clue there was even a problem."
...
The designers fixed the problem simply. They took away the Register button. In its place, they put a Continue button with a simple message: "You do not need to create an account to make purchases on our site. Simply click Continue to proceed to checkout. To make your future purchases even faster, you can create an account during checkout."

The results: The number of customers purchasing went up by 45%. The extra purchases resulted in an extra $15 million the first month. For the first year, the site saw an additional $300,000,000.