missed pop-up and cookies exceptions on every application close

[vimo]

I added some URLs in po-up and cookies exceptions but every time I close and Run Firefox again the exceptions are missed.

ProblemType: Bug
DistroRelease: Ubuntu 11.04
Package: firefox 6.0+build1+nobinonly-0ubuntu0.11.04.1
ProcVersionSignature: Ubuntu 2.6.38-11.48-generic 2.6.38.8
Uname: Linux 2.6.38-11-generic x86_64
NonfreeKernelModules: fglrx
Architecture: amd64
Date: Sat Aug 20 10:42:36 2011
FirefoxPackages:
 firefox 6.0+build1+nobinonly-0ubuntu0.11.04.1
 flashplugin-installer 10.3.183.4ubuntu0.11.04.1
 adobe-flashplugin N/A
 icedtea-plugin 1.1.1-0ubuntu1~11.04.1
ProcEnviron:
 LANGUAGE=it:en
 LANG=it_IT.UTF-8
 SHELL=/bin/bash
SourcePackage: firefox
UpgradeStatus: Upgraded to natty on 2011-04-30 (111 days ago)

[vimo (vimot2)]

Solved.
Preferences -> Security >delete the history when I close Firefox -> Settings -> Unchecked "Web sites Preferences".
Checking the voice, in fact causes the clearing of users web site preferences, including pop-ups and cookies exceptions.