Background image don't show up

HTML-CSS
1

I have added a background image in section tag after the navigation bar. Although I gave all the necessary code.Still background image is not showing up.

Here is my Code link at Gist:
My code

2

Try making your section’s width 100%
Also, make sure your height is actually being accepted (by increasing your 's height) I usually do this:

html, body{
   height: 100%;
}