PXE config file:
default linux
prompt 0

label linux
  kernel centos-4-x86_64-vmlinuz
  append initrd=centos-4-x86_64-initrd.img ramdisk_size=9216 ksdevice=eth0 ks=http://10.10.10.100/build_ks.php 

Anaconda Error:
* ks location: http://10.10.10.100/build_ks.php
* transferring http://10.10.10.100//./build_ks.php
* failed to retrieve http://10.10.10.100///build_ks.php

From 10.10.10.100's apache log:
10.10.10.6 - - [11/May/2006:09:44:33 -0400] "GET /./build_ks.php HTTP/1.0" 404 288 "-" "-"