Responsive design by using media query

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

Most exciting part is using media query and contents alignment.

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

I am seeing that some devices doesn't switch to media query. Even my own cell phone doesn't fire media query. I don't know why.

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

While I inspect my page, some devices don't switch to new media query. If any body can help/guide me, thanks in advance.