Just looking at my site through http://wave.webaim.org/toolbar
Came obvious that there are accessibility problems with the Masquerade form (see image attached).
All forms need to have a label with them. These don't need to be visible, but they do need to be there to provide semantics.
|Masquerade-accessibility-nolabel.png||13.76 KB||Ignored: Check issue status.||None||None|