I use gmail for my E-Mail. When I want to get information from a website it says there is no "e-mail program" please set one up. I do not understan what they mean and what to do.
You might need to change your preference for "mailto" URLs. See whether this works.
orange Firefox button (or Tools menu) > Options > Applications
In the search box, type or paste mail and pause while Firefox filters the list. On the row that says mailto, try selecting Gmail from the drop-down on the right side. The OK out of the dialog and test again.
Does it work?