[Traver]

Whenever I encounter an image or page that cannot be displayed on any site, I am prompted to login like this:

even though I am in fact logged on. When I press cancel, it gives the standard browser error message (this page cannot be displayed, a picture with a red x and so on).
This started last summer at a LAN where I noodled with some configurations to set up the internet, but I have no idea what actually made that thing come up, and thus I have no clue how to remove it, either. Any help to make it go away?

[x..]

I don't understand (language), but you could go:

Start > Connections > Your Connection > Properties

Look for somthing like "Auto-Login" "Auto-Connect", ect.

[Ratty]

Odd. You're just at home with a router and modem, yeah?

I'll have a look into it, but right now, i'm kinda clueless as to why it's popping up o.O

[x..]

I used to get that, I think I fixed it by using firefox?

[Traver]

I don't understand (language), but you could go:

Start > Connections > Your Connection > Properties

Look for somthing like "Auto-Login" "Auto-Connect", ect.

Well, doing this got rid of the actual login box. But it still tries to log in and gives an errormessage when it can't, it just doesn't prompt me for a username and password.
And I am using Firefox.