I'm a user familiar with StackOverflow websites but it took me a while to locate the Ask Question button on AskUbuntu.
Reason: Insufficient contrast (as can be seen below). A single grey / translucent back background should fix the problem.
@jokerdino that has been raised before. I think with the upcoming design changes, I will. The current AU site design was done by a Canonical designer back in 2010.
I may make Ask Question link part of the other top nav items. and give it a more prominent treatment.