Getting rid of the ‘blocked pop-up’ yellow bar in Firefox
Some people prefer it, if Firefox does not display a yellow alert bar in the browser, when a pop-up window has been blocked, citing a preference of pop-ups to be blocked “silently.” You can get rid of it, by modifying a hidden setting.
In Firefox, go to the URL: about:config
Search for the preference privacy.popups.showBrowserMessage.
Double-click on it, which should modify the value to false.