Basically, the site takes her Masters thesis study of 75 ecommerce sites and makes it more accessible online. (For the impatient, you can download the 8mb pdf of Heidi's thesis).
I met Heidi at the IA Summit in Portland, and think that this will be a great resource for the community. I'm hesitant about considering common practice to be best practice (as gets implied in surveys like this), but it's good to consider if something really is a de facto standard, and what reasons your own project has for doing things differently. [ia/ – information architecture news]