url() function for HTML background

div {  background:url(smiley.gif) top left no-repeat }

What is this url()? I can't find documentation online.

(See http://www.w3schools.com/cssref/css3_pr_background开发者_开发问答.asp.)

In your example url is the url of the image that will be used as the background for the div tag.

MDN has a decent explanation of it: https://developer.mozilla.org/en/CSS/uri

MDN is usually more up-to-date than W3Schools.

It's the URL of the background image.

For example, lets say you've your images stored at /images and you've a background image called background.png located at /images/background.png, then you do:

background-image: url('/images/background.png');

the background of the div will be image from file called smiley.gif you should have a file called smiley.gif at the same directory of your html file

Here is the page that mentions url: http://www.w3schools.com/cssref/pr_background-image.asp Other than that, url is simply a url string pointing to the image.

it's not HTML, yes CSS(Cascading Style Sheets). the url () function set the background image for an element.