The media queries look ok. To test:
- In Firefox: Go to Tools -> Web Developer -> Responsive Design. It will
put a wrapper around your webpage and you can select the resolution, up to
- In Chrome: Go to Tools -> Developer console. Open the developer
settings (the gear icon in the lower right corner). Click on the
"Overrides" section. Check the "Device Metrics" box and set the screen size
to the one you would like to test for.
- In IE9+, go to the F12 developer tools and go to the "Tools" menu. You can
set device resolution there.
Changing these settings will re-render the page and trigger your media
queries if they are correct.