How can I disable “add application for mailto links” bar in Firefox?

Question

Every time I log on to my webmail I see a bar like on image below. I don't want to add this as an application and it is pretty annoying to close this every time. How can I disable it permanently?

The bar says:

Add o2 Poczta (poczta.o2.pl) as an application for mailto links? [Add Application] x

Image:

EDIT:
I tried to use Firebug to see what causes this bar to appear but with no luck. Anyone help?

EDIT 2:

Su's answer from http://webmasters.stackexchange.com :

This is done by registering a protocol handler. From that page:

navigator.registerProtocolHandler("mailto", "https://www.example.com/?uri=%s", "Example Mail");

The site would just have to run a similar snippet at an appropriate moment(login, in your case).

Link: registering a protocol handler

How can this be blocked?

Answer 1

have you tried going to about:config

There are some keys in there relating to mailto:

network.protocol-handler.external.mailto;true
network.protocol-handler.expose.mailto;false
network.protocol-handler.warn-external.mailto;false

You could try toggling them, I can't test as I can't recreate whats happening for you, I think maybe the first of the three to false maybe a good start,

Be careful when editing this config as it may cause strange things to happen maybe even break firefox.

Answer 2

you can do it easily with adblock-plus addon for firefox (assuming you are polish you probably using it anyways :P ) or ad-block plus for chrome. And you get the nice advantage of all the ads blocked for you as well everywhere (even in youtube videos you no longer see commercials)

all you need to do is google search for ad block plus. download it install it

Who knows maybe its going to disappear as soon as you download the addon if not then find the name of the divider that the annoying popup appears I assume you know how to do that since you are familiar with firebug

then go to filter preferences ctr+shift+F

then go to custom filters tag then go to Element hiding rules (the last one) then click add filter then type #div(div_name)

div_name = the actual name of the div

and you are done. If something is an image and you want to block it you can right click it and there will be an option but im assuming this is not an image but a whole divider you want to get rid off.