Please can you advise another important extension?
For what?
AVG Secure Search - addition to the popular web browsers for secure online search. Warn users before they visit a malicious Web site to protect your personal data and your computer from online threats
AVG LinkScanner real-time checks web pages visited by the user, for the presence of malware and other Internet threats
Dr.Web LinkChecker - a free plug-in for popular web browsers designed to test web pages and files downloaded from the Internet
McAfee SiteAdvisor - free plug-in for web browsers Firefox, Google Chrome and Internet Explorer, which provides information about the level of security of visited web sites. The plugin detects sites containing spyware, spam and fraud
Ad-Aware Security Toolbar protects you from dangerous websites. Free plug-in for web browsers checks in real time URL-links using a constantly updated list of malware and phishing websites
NoScript - plug-in that provides additional protection for the web browser Firefox. The plugin allows execution of JavaScript, Flash, Java-only sites that you set
With AVG Privacyfix, plug-in for Google Chrome and Firefox, you can control privacy settings in Facebook, Google and other Web sites that you visit, and also block tracking your online activities on the Internet
Ghostery plug-in for web browsers Firefox, Safari, Chrome, Opera, Internet Explorer, detects and allows you to control and block tracking sites, advertising networks, web publishers, etc., embedded in the Web pages of sites
etc.