Hi, so i have been curious what is the purpose of this and i enabled it.

First i have google, second Yahoo.
And i must say that using webpagetest.org i see webpage loads like 2-3 seconds faster if that is not luck

http://yui.yahooapis.com/combo

At Custom Remote YUI Path i have:
http://ajax.googleapis.com/ajax/libs/yui/


And at Custom Remote jQuery Path:
ajax.googleapis.com/ajax/libs/jquery/{version}/jquery.min.js