Interesting tool...
Just for fun, I scanned a very busy and important e-commerce site, that of Southwest Airlines (www.southwest.com) - it got a D-.
Another site, a large multinational sporting goods company's US site (Rapala - usa.rapala.com) - it got an F.
Do you think any of the do-it-yourself website builder tools (like squarespace.com) even possess the tools to make what you build capable of achieving an A on this test?