Responsive techniques; Html5 and Css3

What are you most proud of, and what would you do differently next time?

I'm programming again after six months off, so the time that i made this website was very cool for someone that is so time off. I'd apply new tags and techniques that i forgot how to do.

What challenges did you encounter, and how did you overcome them?

I forgot how to centralize a div, but i searched in Google and found the solution.

What specific areas of your project would you like help with?

Quality of my CSS, i don't know if the techniques that i used to centralize the div was good.