If you mean like Internet Explorer "Content Advisor" that allows you to add sites to allow or block list; establish ratings; and secure these with a password then no.
Firefox does have a add-on BlockSite 0.6
https://addons.mozilla.org/en-US/firefox/addon/3145
BlockSite is an extension, which automatically blocks websites of your choice. Additionally, this extension will disable all hyperlinks to these websites, by just displaying the link text without the clicking functionality. This extension should by no means be used for parental control or access control purposes, just because it isn't secure and can easily be disabled or even removed. This extension adds the site blocking functionality that was removed from Adblock Plus.
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If you are trying to protect you children this is a poor approach. They can install one of dozens of browsers and hide or remove the start icon so you will not be aware it is there.
You could use the hosts file to block sites but this is easily defeated.
Blocking Web Pages With the Hosts File
http://bucarotechelp.com/computers/winadmin/97072610.asp
http://www.overclock.net/faqs/44143-how-use-hosts-file-block-websites.html
http://www.mvps.org/winhelp2002/hosts.htm
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Your internet service provider probably provides a method to control access to the internet. I have ATT they have parental controls to limit access. You can restrict the types of web sites, as well as specific web sites, that your children can access. Each user can have a separate account. A master password is required to change settings. Settings allow selecting for each user: Allowed times during the day; maximum hours of use; set ratings for types of content allowed to be viewed.
Restricting Access
Lockdown PC
http://pcworld.about.com/magazine/2204p103id114727.htm
Windows XP passwords:
All accounts must have passwords. Each person must have a separate username and password to sign on the computer. You must have an “Administrative” account. Everyone else should have “Restricted Access” accounts.
Do not enable automatic logon.
http://www.dummies.com/WileyCDA/DummiesArticle/id-350.html
http://www.microsoft.com/windowsxp/using/setup/winxp/accounts.mspx
http://www.microsoft.com/windowsxp/using/setup/winxp/switchusers.mspx
Turn off the guest account
http://www.microsoft.com/windowsxp/using/setup/tips/soleuser.mspx
Protect your computer from access when you are temporarily away from your computer by using a screen saver password
http://www.microsoft.com/resources/documentation/windows/xp/all/proddocs/en-us/display_assign_screensaver_password.mspx?mfr=true
Each person (if you allow) should have a separate email account.
A determined person can break or disable or get around all passwords.
--How to make files and folders private in Windows XP so that only you have access to them
http://support.microsoft.com/kb/930987
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Vista Parental Controls
http://windowshelp.microsoft.com/Windows/en-US/Help/585539d0-0862-41e4-9b39-53467648efc51033.mspx
http://www.lockergnome.com/nexus/it/2007/02/20/vistas-parental-controls-part-i/
Restricting Internet Access
Your internet service provider probably provides a method to control access to the internet. I have ATT they have parental controls to limit access. You can restrict the types of web sites, as well as specific web sites, that your children can access. Each user can have a separate account. A master password is required to change settings. Settings allow selecting for each user: Allowed times during the day; maximum hours of use; set ratings for types of content allowed to be viewed.
http://help.yahoo.com/sbc/tutorials/olp/tut_olp_index.html
http://help.yahoo.com/sbc/tutorials/ypc/pc_timer1.html
Yahoo Parental Controls
http://help.yahoo.com/sbc/tutorials/ypc/start_pc1.html
I am not recommending this software, but it pages clearly show setting up internet profiles and customizing the restrictions.
http://www.pchomesoft.com/keywords.html
http://www.pchomesoft.com/limit_kids_control_guide.html
http://www.pchomesoft.com/images/kta2.gif
http://www.pchomesoft.com/images/kta1.gif
Software downloads. Some free, some offer a limited trial.
http://www.download.com/3120-20_4-0.html?tg=dl-20&qt=parental&tag=srch
Reviews of programs that restrict net access:
http://www.pcmag.com/article2/0,1895,1986753,00.asp
http://www.consumerreports.org/cro/electronics-computers/internet-filtering-software-605/ratings/index.htm?resultPageIndex=1&resultIndex=3&searchTerm=parental%20controls
http://www.filterreview.com/pages/table1.htm
http://www.geek.com/news/geeknews/2001feb/gee20010215004355.htm
http://internet-filter-review.toptenreviews.com/
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Monitoring Software
http://www.monitoringsoftwarereviews.org/
http://www.pcmag.com/category2/0,1874,1639158,00.asp
http://familyinternet.about.com/library/weekly/aa041901a.htm
http://monitoring-software-review.toptenreviews.com/
http://ask-leo.com/parental_monitoring_software_my_child_figured_out_how_to_turn_it_off_what_can_i_do.html
http://ezinearticles.com/?Monitoring-Software---What-You-Need-To-Know&id=454291
http://www.freesearching.com/monitor.htm
http://dmoz.org/Computers/Internet/Child_Safety/
http://www.download.com/3120-20_4-0.html?tg=dl-20&qt=parental&tag=srch
How To Record All Microsoft Messenger conversations (free)
http://www.protectiveparenting.com/web/html/modules.php?name=News&file=article&sid=12
http://www.msgpluslive.net/
How can I keep my kids safe from internet garbage
http://ask-leo.com/how_can_i_keep_my_kids_safe_from_internet_garbage.html
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protectiveparenting.com
http://www.protectiveparenting.com/web/html/modules.php?name=Topics
Free Publications:
Help with IM, Chat, AIM, etc.
Publications: Chat Conversation Logging
Publications: Disabling Chat
Publications: Chat Code Words and Acronymns
Publications: Web-based IM and Chat
Publications: Blogging and Forums
Lock down your computer
Publications: BIOS Password Protection
Publications: Prevent Children from Installing Programs
Publications: Setting Up User Accounts in Windows XP
Web filtering and control
Topic: Web filtering and control
Publications: Restrict web sites on Windows XP
Publications: What is a Proxy?
Publications: Lock down Internet Explorer History
Selecting Filtering Software For Your Family
http://familyinternet.about.com/cs/filteringsoftware/a/aafiltering.htm
Parent's Guide to Children's Online Safety
http://www.usdoj.gov/criminal/ceos/onlinesafety.html