Understand that no dialog is necessary for such an idea to be implemented at all.
The webpage you are viewing may
not work correctly because the following
options differ from their default values:
1. Enable automatic loading of images.
These features of Firefox are essential
for most webpages to run properly. If the
webpage you are trying to access is behaving
strangely or appears to be working incorrectly,
<a href="">click here</a> to load the page
with the default browser configuration.
Also: how is that not a dialog? It presents a message to the user, and waits for a reply.