Create a unique GUID. I sometimes use these when I need a unique value; for instance, when I need to add a unique ID to a DIV.

guid.js

function CreateGuid() {
    function _p8(s) {
        var p = (Math.random().toString(16) + "000000000").substr(2, 8);
        return s ? "-" + p.substr(0, 4) + "-" + p.substr(4, 4) : p;
    }
    return _p8() + _p8(true) + _p8(true) + _p8();
}

// to create a GUID, just call it like this:
// var id = CreateGuid();
// that's it!