What triggers "A script modified the host part ..." warning?

[novakyu]

Hi,

I apologize in advance if I'm asking a common question (I skimmed last
few months of archive and didn't find anything), but how do I find out
what triggers the warning, "A script modified the host part in a link
in the page. This can cause serious privacy problems." ? This warning
shows up in A LOT of places, including GMail and my own website (which
I designed to be as little dynamic as possible), but without being
able to find out exactly what triggers this, it's kinda useless.

I am using IceCat on Debian Etch. I compiled it (after running apt-get
build-dep iceweasel) from the source distribution, version
2.0.0.11-g1, the latest, I think.

Thank you,

Andrzej