Enter one mapping per line, in the format <URL>[|<extensions>]:
http://cdn-a.com
However, you can also enter multiple URLs, the files will then be distributed randomly (yet consistently, meaning that the same file will always be served from the same URL) from the different URLs! E.g.: http://cdn-a.com http://cdn-b.com
Note that if you want to save just a few more bytes, you should use protocol-relative URLs: //cdn-a.com
instead of http://cdn-a.com
(this works fine in all browsers)..css .jpg .jpeg .png
http://cdn-a.com
http://cdn-a.com|.css .jpg .jpeg .png http://cdn-b.com|.zip http://cdn-c.com
http://cdn-a.com|.css .js http://cdn-b.com http://cdn-c.com|.jpg .jpeg .png http://cdn-c.com