Please install Firefox 18.0.1, the Firefox 4 you are using is extremely old and out of date. Update Firefox to the latest release

Then, the message you are seeing is likely because of missing plugins (flash in your case) instead of missing add-ons (Firefox doesnt prompt you to install add-ons to view a webpage, that isn't necessary). Install Flash to take care of that message, http://ninite.com/flash/ninite.exe

But they are not necessary for me. I don't want to install flash. And I want firefox to stop telling me that I need it to see all content on the page. Because I don't care.

(Please update, it is necessary)

So far as I know there is no way to turn off the option to install the plugin, but just ignore it then if you don't want to install flash.

I don't know why it says that I use firefox 4... When I check in my About window it says 18.

I do ignore the message about the plugins. But I've started to get a little bit annoyed that I have to move up and press the little x every time I navigate to a site that needs something like flash. It eats up the size of about two text rows... it feels so unnecessary that it's there. If I want flash I will install it... The browser doesn't have to inform me about it every time.

I really hoped for a better answer. Hopefully the firefox crew will add an option to not show that kind of messages in the future.

Try the steps at How to reset the default user agent on Firefox

Ah... yes. That seemed to be wrong. Thank you... didn't solve my initial problem though.. :)