All browsers provides options for enabling or disabling the popup blocker like for example in IE Popup blocker and google chrome popup blocker. Similarly Opera also provides Popup blocker options and this can be accessed using the preferences menu.
Click the menu drop down and navigate to Settings menu. From the list of available menu click the Preferences menu.
In the Preferences Window, under General tab, navigate to Choose how you prefer to handle pop-ups section.
Using the Pop-ups dropdown, you can set your desired pop-up blocker settings. The list of available values for Pop-ups are Block unwanted pop-ups, Open pop-ups in background, Open all pop-ups and Block all pop-ups
After selecting the desired value for Pop-ups dropdown, click Ok button to save the changes.