When I registered here earlier today, I did so through the Mobile Site from my phone. Whilst registering, the text I entered in each field blended fully in with the background, and so I was unable to read what I had written. When I first attempted registration, this caused me to apparently mis-type my e-mail address, and so my confirmation was impossible. I then re-registered through the Classic Site.
I would recommend that the text colour of the entered fields be changed in the mobile site, as this was highly frustrating (and forced me to alter my first preference of username).