Reid at Davis Frame timber frame homes poses the question why so many usability gurus talk about the importance of left-hand nav, when their own sites feature top navigation only!

I think you can have it either way depending on the complexity of the site, since peoples’ eyes sweep across in an “F pattern” – left to right across the top (thus your typical top nav) then again left to right a little farther down (headline and important “above the fold” content), then down along the left side (thus, left nav). You've probably seen the eye-tracking heat patterns before, from researchers like usability guru Jakob Nielsen. So there is some rationale for sites using top-navigation only, but I can’t think of many websites that are so simple as to be able to get away with it.

I just noticed this morning that Amazon has redesigned its header away from their famous tabbed approach, presumably to make it less noisy/confusing and get more stuff above the fold. I haven’t heard a thing about this – I wonder how new it is. The Netflix approach to navigation is interesting in that they have flopped the equation to go with a top-and-right nav.

My guess with both of these merchants is they want to put more emphasis on content (products, movies) and less emphasis on navigation. Emphasizing navigation has always been a priority for sites that get a lot of first-time visitors who need to quickly assess what a site is about and where to get things. Sites with a lot of repeat visitors (like Netflix and Amazon) have different priorities -- assuming people are fairly familiar with how to get around, they want to help the visitor focus on product headlines, images, and buy buttons.

Of course, Netflix has a totally different priority if you’re not cookied/logged in: then it’s all about the free trial signup form. Perhaps that radical new-user-versus-repeat-customer design strategy should be part of anyone's website.