The Spaghetti Refactory Established 2015

Device Emulators all up in your browser

File this one under the "n00b" tag.

For checking responsiveness on mobile, Chrome (and probably Firefox) has some sweet device emulators.

Go to Developer Tools, then click the little phone icon in the far left of the Developer Tools nav
and it will let you select whatever device to see how the current page looks.

Wow. Much responsive. Very browser.