I don't know why you're being downvoted. This is correct. Landing pages can and should be a/b-tested to the death. If you're gonna a/b-test anything, it's gotta be your landing page!
Many people have an opinion about the perfect landing page based on some narrow experience. See http://www.google.com/search?q=perfect+landing+page for examples. Absorbing these guidelines provides a good starting point for any landing page optimization campaign, but only a starting point.
Claiming you have created a "perfect" landing page is simply wrong. There is no such thing as a perfect landing page. Through rigorous A/B/n & multivariate testing you can identify pages with better conversion rates and discard poor performers. It is also important to note that this optimization is not necessarily transferable to different ad messaging, user segments, products, or conversion goals.
#10 on their list, in fact, discuss A/B testing.
However, that advise alone is useless. Testing whether A or B is better is useless if both A and B don't have a good foundation.