I have just upgrade from 1.8.2 to 1.8.4 and notice the following

I have 2 host with web monitored setup

Host A
1) monitor http://xyx.abc.com/test.asp with required (work fine)
2) monitor http://xyx.abc.com/default.htm with required - works in 1.8.2 does not work anymore if keep return value 1 whereas the download/response data works fine.

Host B
1) similar to Host A 2) http://ctx.abc.com without required works in 1.8.2 but does not work anymore in 1.8.4.

I tried to recreate Host A 2) ane Host B 1) also it does not work.

Refer to http://www.zabbix.com/forum/showthread.php?t=20928 for more information.