Netcraft do not display uptime graph, why?

[Byung-Hee HWANG]

Hi there,

My machine is FreeBSD 6.x currently. But Netcraft do not display of my
machine's uptime graph. When I used FreeBSD 4.x, actually I could see
the uptime graph in Netcraft.

What happened? 
And what can I do to solve the problem?

Here is my machine's uname:

bh at setaria:~> uname -v
FreeBSD 6.2-RELEASE-p7 #4: Thu Aug 30 23:44:27 KST 2007     
root at setaria.izb.knu.ac.kr:/usr/obj/usr/src/sys/SMP 
bh at setaria:~>

Byung-Hee