A lot of content on the web could potentially offend.

I do not think firefox itself has any particular features that will help you, with regard to images, or advertisements, other than blocking sites that are not who they claim to be.

Firefox does have a setting to block "pop-ups" which may help in some circumstances. See Pop-up blocker settings, exceptions and troubleshooting

I suspect if you wish to have tighter controls you will need to look to third party add-ons or software.

This forum is here to assist firefox users, but is concerned with the practicalities of solving individual user's problems, not with broader concerns about internet policy and use.

also try download adblocker that is a god send to me you'll find it on your ubuntu software centre just type Adblock plus extension for firefox

Do a malware check with some malware scanning programs.
You need to scan with all programs because each program detects different malware.
Make sure that you update each program to get the latest version of their databases before doing a scan.

• http://www.malwarebytes.org/mbam.php - Malwarebytes' Anti-Malware
• http://www.superantispyware.com/ - SuperAntispyware
• http://www.microsoft.com/windows/products/winfamily/defender/default.mspx - Windows Defender: Home Page
• http://www.safer-networking.org/en/index.html - Spybot Search & Destroy
• http://www.lavasoft.com/products/ad_aware_free.php - Ad-Aware Free

See also:

• "Spyware on Windows": http://kb.mozillazine.org/Popups_not_blocked

It may help to give a screenshot of what is happening, or to give some examples of the websites involved:

• the websites you use, such as: webmail, shopping sites, modern videos/pop music sites; when this occurs
• the websites the inappropriate advertisements promote

I am not sure if the inappropriate adverts may be the standard advertisements on many sites, or whether they may be due to possible malware.

Is the problem that

1. you expect K9 to bark! or to block something, so that content is appropriate for a young child, but it is failing to do this adequately;
2. or you are getting totally unexpected and possibly pornographic pop-ups that adults may object to.

It is the 2nd type of problem that is more likely to be caused by malware. The 1st type of problem may just be commercial adverts, and K9 may be too long in the tooth to catch all these.

You're using Windows 7, so you can use Parental Controls to place limits on what your kids can view. See Windows 7 Parental Controls