errors with Firefox installation

[Ali Faiez Taha]

Dear Sir.
Iḿ trying to install Firefox 18.0_1 (pkg_add -r firefox), but there are many errors.
When I run firefox the error is:

$> firefox
XPCOMGlueLoad error for file /usr/local/lib/firefox/libxpcom.so:
/lib/libc.so.7: version FBSD_1.2 required by /usr/local/lib/firefox/libxul.so not found
Couldn't load XPCOM.

More informations:
* uname -a
FreeBSD granito2.cirp.usp.br 8.3-STABLE FreeBSD 8.3-STABLE #1: Wed Jun 13 23:41:51 BRT 2012
root at granito2.cirp.usp.br:/usr/obj/usr/src/sys/GRANITO2  i386


* Output from 'ident /usr/ports/www/firefox/Makefile'
/usr/ports/www/firefox/Makefile:
     $FreeBSD: ports/www/firefox/Makefile,v 1.287 2013/01/11 11:12:40 svnexp Exp $


When I use make, the compilation stops and abort.

What I need to solve this ?

Thanks a lot.