Use this simple, 25-point checklist to assess critical website usability issues. Includes free download (1-page PDF).
The list is split into 4 roughly equal sections, (I) Accessibility, (II) Identity, (III) Navigation, and (IV) Content. I'll describe and rationalize all of the sections and line items below, but you can also download the checklist as a simple, 1-page PDF. I try to keep it simple with 3 basic ratings: (1) Green Check = Good/Pass, (2) Red Check = Needs work, but no disaster, (3) Red X = Bad/Fail. Not all points are necessarily applicable to all sites.
Via Dennis T OConnor, Mark E. Deschaine Ph.D.