Display resolution maximum for Centos 5.5 is 1024 x 768, the browser window in Firefox 5.0 is too large.
Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.11) Gecko/20101028 CentOS/3.6-2.el5.centos Firefox/3.6.11
$ cat /etc/*release CentOS release 5.5 (Final)
$ uname -r 2.6.18-194.17.4.el5
Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.11) Gecko/20101028 CentOS/3.6-2.el5.centos Firefox/3.6.11
$ cat /etc/*release
CentOS release 5.5 (Final)
$ uname -r
2.6.18-194.17.4.el5
Opaite Mbohovái (1)
Do you mean that you see a horizontal scroll bar or does the window extend beyond the display width?
Can you resize that window via the system menu (Alt + Space)?
If you can then close Firefox to see if that saved the screen dimensions.