Knowing how to block and unblock sites in your operating system can come in very handy, mostly if you have children you want to protect from accessing inappropriate content. Regardless of the reason why you would like to block and unblock sites, being able to perform this task will ultimately help you take control of your network and protect your computer from websites you consider useless or potentially harmful. Fortunately, blocking and unblocking sites is a simple task you can perform swiftly through your Web browser's Internet Options setting.
Launch your Internet Explorer browser and select the "Tools" option, which is displayed on the upper right corner of the browser's window. Click on the "Internet Options" selection displayed at the bottom of the drop-down menu and then select the "Security" tab. Select the red icon titled "Restricted Sites," which is displayed in the box below where it says "Select a zone to view or change security settings." Click the "Sites" tab featured below the "Restricted Sites" icon you just clicked on. Type the URL address of the site you would like to block in the text field displayed below where it says "Add this website to the zone:" and then click the "Add" tab to save the changes (you may block an indefinite number of sites). If you wish to unblock any of the sites you have blocked, simply go back to the "Restricted Sites" menu, click on the site you would like to unblock, which will be displayed below where it says "Websites:" and click on the "Remove" tab. use security zones in Internet Explorer http://support.microsoft.com/kb/174360
b> Using Firefox
Launch your Firefox Web browser and open the support page for Mozilla Firefox (see Below). https://addons.mozilla.org/en-US/firefox/search/?q=parental+control&cat=all
In this Web page you will be able to access an array of filtering add-ons you can utilize with Firefox to block and unblock any sites you want. Look through the various filtering add-ons available on the Mozilla Firefox support page and click on the option you would like to use to block and unblock sites. Keep in mind that some of the filtering add-ons require a payment and some don't. Click on the prompt that says "Continue to Download" or "Add to Firefox." The prompt that will be displayed to you will ultimately depend on the filtering add-on you chose; however, you will have to click on either options to download the add-on. Select the tab that says "Install Now," which will be displayed on a pop-up window. You may want to consider downloading the the FoxFilter add-on because it has the reputation of being prolific and it is free to use. Restart your Firefox Web browser once you are prompted to do so. This will occur after the installation process has finished. Once Firefox restarts, the Firefox filtering add-on you chose will be enabled and you will be able to block and unblock sites through the add-on.