How to Block Websites in Opera Browser? Open Opera browser on your computer. Click on the opera icon at the top of the browser. Hover your mouse on the settings tab and select “Preferences.”. Preferences dialogue box will appear. Click on the “Advanced” tab. Choose “content” in the left-hand panel. Now, click on the button ” Blocked Content” Click on the add button. Type in the URL of the website you want to block. Click ok button. Now try accessing the web page. As you can see the web page is now blocked in opera. You can’t access that Website now.