They may make sense to you and help you get the job done, those design rules you follow. But to someone else they may sound like nonsense. Ridiculous Design Rules collects design, advertising, and fashion rules that make no sense to contributors. Some look perfectly valid to me, like that about using Helvetica. Some do look odd.
The site even offers a book for every flavor of rules. I think I want the one for design, Never Use White Type on a Black Background. The preview looks sweet.