# CSS Object Model (CSSOM)
# Adding a background-image rule via the CSSOM
To add a background-image rule via the CSSOM, first get a reference to the rules of the first stylesheet:
var stylesheet = document.styleSheets[0].cssRules;
Then, get a reference to the end of the stylesheet:
var end = stylesheet.length - 1;
Finally, insert a background-image rule for the body element at the end of the stylesheet:
stylesheet.insertRule("body { background-image: url('http://cdn.sstatic.net/Sites/stackoverflow/img/favicon.ico'); }", end);
# Introduction
The browser identifies tokens from stylesheet and coverts them into nodes which are linked into a tree structure. The entire map of all the nodes with their associated styles of a page would be the CSS Object Model.
To display the webpage, a web browser takes following steps.
# Remarks
The CSS Object Model (CSSOM) is a specification on its own.
The current draft can be found here: https://www.w3.org/TR/cssom-1/ (opens new window)