[Black Tiger]

It's easyer then you think. Just answer the questions to yourself and take the appropriate action:

1.) Are you using a control panel on your server. On most servers this can be either Cpanel, Directadmin or Plesk. Others are also possible, but not that much used as these 3.
a.) if the answer is yes, you probably don't want to use the yum install command, so goto b.)
If the answer is no, goto 2.)
b.) If you are using Cpanel, you have to let Cpanel compile your GD. If you don't know how this works, ask professional support.
Same goes for Directadmin and Plesk.

2.) Use the yum install php-gd command I gave you.
if that command does not work, use the yum install gd command I gave earlier.

3.) /etc/rc.d/init.d/httpd restart
or
/sbin/service httpd restart

I'm going to sleep now, it's 04.12 AM over here, if you want me to fix it for you, I would be glad to help you. Send me a pm and I fix it for you tomorrow afternoon.
Thats somewhere around 14.00-15.00 GMT+1, so in about 10 hours from now. I do need login credentials then.