Explain toolbarqueries.google.com

I heard alot of people talking about http://toolbarqueries.google.com/, now this may seem dum on my part, but how in the world does that thing work. And what makes so different then the others?

 

Its the server that gives the PR value to your browser toolbar.

 

do ANY ONE KNOW HOW TO CALCULATE CHECKSUM VALUE CH OF http://toolbarqueries.google.com ?

 

function makehash(u) {
	var zF = function(a, b) {
		var z = parseInt(80000000, 16);
		if(z & a) {
			a = a >> 1;
			a &= ~z;
			a |= 0x40000000;
			a = a >> (b - 1);
		} else
			a = a >> b;
		return a;
	}, mix = function(a, b, c) {
		a -= b; a -= c; a ^= (zF(c, 13));
		b -= c; b -= a; b ^= (a << 8);
		c -= a; c -= b; c ^= (zF(b, 13));
		a -= b; a -= c; a ^= (zF(c, 12));
		b -= c; b -= a; b ^= (a << 16);
		c -= a; c -= b; c ^= (zF(b, 5));
		a -= b; a -= c; a ^= (zF(c, 3));
		b -= c; b -= a; b ^= (a<<10);
		c -= a; c -= b; c ^= (zF(b, 15));
		return new Array((a), (b), (c));
	}, GoogleCH = function(url) {
		length = url.length;
		var a = 0x9E3779B9, b = 0x9E3779B9, c = 0xE6359A60, k = 0,len = length, mx = new Array();
		while(len >= 12) {
			a += (url[k+0] + (url[k+1] << 8) + (url[k+2] << 16) + (url[k+3] << 24));
			b += (url[k+4] + (url[k+5] << 8) + (url[k+6] << 16) + (url[k+7] << 24));
			c += (url[k+8] + (url[k+9] << 8) + (url[k+10] << 16) + (url[k+11] << 24));
			mx = mix(a, b, c);
			a = mx[0];
			b = mx[1];
			c = mx[2];
			k += 12;
			len -= 12;
		}
		c += length;
		switch(len) {
			case 11: c += url[k+10] << 24;
			case 10: c += url[k+9] << 16;
			case 9: c += url[k+8] << 8;
			case 8: b += url[k+7] << 24;
			case 7: b += url[k+6] << 16;
			case 6: b += url[k+5] << 8;
			case 5: b += url[k+4];
			case 4: a += url[k+3] << 24;
			case 3: a += url[k+2] << 16;
			case 2: a += url[k+1] << 8;
			case 1: a += url[k];
		}
		mx = mix(a, b, c);
		return mx[2] < 0 ? 0x100000000 + mx[2] : mx[2];
	}, strord = function(string) {
		var result = new Array();
		for(i = 0; i < string.length; i++)
			result[i] = string[i].charCodeAt(0);
		return result;
	};
	return GoogleCH(strord('info:'+u));
}

Code (markup):

source: google pagerank status extension from chromium.

regards