I needFirefox redirect the pages to another to complete a work operation and i do not know how to do it. In spanish, please

In Internet Explorer i can to begin an operation in a site linked with another to continue and to obtain due permission, and with the button "continue" in the second window, to return to the first site and to end the operation (the web sites are differents organizations). In Firefox the button "continue" is disable ¿why? I look for "to allow or permit the pages to redirect" or the exceptions to redirect and there is nothing about. Excuse me for my English, i am a spanish speaker.