It works mainly for google.com, but it doesn't work quite well for other google sites like gmail. I suggest making a general locale forcer for global google services or even better for most mainstream websites, that would make your plug-in a must for many. Thanks for your time.

Thanks for this add-on!
This is an easy and effective solution to the common problem, that Google will by default choose a display language for you. (You can change that, but it requires cookies; this add-on does not require cookies!)