You can test the parent.location
value:
if(parent.location == 'http://cargocollective.com/')
{
var url ='http://cargocollective.com/clairelefevre/about';
var delay = 6;
var d = delay * 1000;
window.setTimeout ('parent.location.replace(url)', d);
}
But honestly, it's not very clean IMO. What I would do is put a hidden input in your homepage, with a id and value. Test if the user is on the homepage by testing this input.
You can also check the location.pathname
value.
if(parent.location.pathname == '/')
{
//your code
}