I'm a user familiar with StackOverflow websites but it took me a while to locate the Ask Question button on [AskUbuntu][1].

Reason: Insufficient contrast (as can be seen below). A single grey / translucent back background should fix the problem.

![top right of askubuntu theme][2]


  [1]: http://askubuntu.com/
  [2]: https://i.sstatic.net/pIUJt.png