Jacob Nielsen recently reported how even key areas with eye popping fonts can be easily ignored if they are designed like promotional banners. Another good reason to take another look at the design of key elements on your store including your search box, add to cart button, and newsletter sign up. If you really want to know what your customers think, get others to look at your site (spouse, children, friends, relatives or even strangers).
You'll also want to look at his previous report on banner blindness.

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