[css] Insert a background image in CSS (Twitter Bootstrap)

Is your image on the same folder/directory as your css file? If so, your image url is correct. Otherwise, it's not.

If by any chance your folder structure is like so...

webpage
-index.html
-css
- - style.css
- images
- - background.png

then to reference the image on your css file you should use the following path:

../images/background.png

So that would be background: url('../images/background.png');

The logic is simple: Go up one folder by typing "../" (as many times as you need). Go down one folder by specifying the folder you wish to go down to.