The problem of building mozilla 1.7.8

[Xu Qiang]

Hi, all: 

I am trying to compile mozilla 1.7.8 from src in my FreeBSD 5.3 (i386) PC. 

Yet, when I run the configure script, I met this error: 
-----------------------------------------------
checking for libIDL - version >= 0.6.3... no
*** The libIDL-config script installed by libIDL could not be found
*** If libIDL was installed in PREFIX, make sure PREFIX/bin is in
*** your path, or set the LIBIDL_CONFIG environment variable to the
*** full path to libIDL-config.
checking for orbit-config... no
configure: error: libIDL not found.
        libIDL 0.6.3 or higher is required.
-----------------------------------------------

But I already have had libIDL installed, the version is 0.8.4, isn't it higher than 0.6.3?

Regards,
Xu Qiang