1: I had installed lighttpd-1.4.18-1.el4.rf and lighttpd-fastcgi-1.4.18-1.el4.rf.i386.rpm.
2: Run installer script.
3: Run installer script again without un-installing any thing.

Installation ends with error "package lighttpd-1.4.18-1.el4.rf is already installed
warning: lighttpd-fastcgi-1.4.18-1.el4.rf.i386.rpm: V3 DSA signature: NOKEY, key ID 6b8d79e6
package lighttpd-fastcgi-1.4.18-1.el4.rf is already installed
something wrong while installing lighttpd rmp. Please check
Dimdim preinstall checks not successful. Please check documentation

and on checking the log file message is

Checking lighttp version
Inside lighttpd function - version required 1.4.18
Downloading from the repositroy for lighttpd
Downloading from the repostiory complete
One package for lighttpd install is available for install
Both lighttpd rpm packages are available for install
Installing the downloaded lighttpd rpm packages
One of the downloaded package is not proper for lighttpd
Check failed in lighttpd

This issue is raised in sf.net url is "https://sourceforge.net/forum/message.php?msg_id=4648185".