Your thoughts on this design

Hello

I'm newbie with this of design and code, so I'd like to know what do you guys think.

This is a forum software that I'm creating, it's being made in PHP, for the design I use boostrap, some guys told me about semantic-ui but I don't know too much about that yet.

I'm trying to keep the design as simple as possible, using only fontawesome, js and css, without using images.

At this moment I only have done the registration and login page so that's what I'm gonna show you

Register page



Bootstrap inbuilt responsive stuff



Any comment is welcome