How many steamgift page I can open before my browser crash ?

You should test different browsers and tell us who's win...

one time i tried this on my galaxy s4 with chrome browser.i opened about 60 tabs...my battey started depleting like one percent every minute and phone was getting hotter every second!

I said 358, so I was close!

As a side note, I think you have entirely too much free time on your hands :P

I hope c.a. 52. I didn't try more. I'd rather to close previous with GA I entered and then open another series of cards.

Pretty nice thing to check, thanks for doing this for us! :)
Also, thanks for the impossible thing!

The answer is 42.

Opened 100 tabs and nothing unusual happened, too lazy to proceed further.

You shoulda tried this some weeks ago. You coulda opened thousand of them and it wouldn't matter because none of 'em would load :D
(SG had some issues a while back)

I think it also depends on how fast you open them...

I tried up to 138 if it will please you.

Usually I have around 50 tabs opened in my firefox. Although yesterday I prepared my system for a format and now I have only 8. I'm not happy with the last update since it seems Firefox consumes a lot more memory after some hours.

I have no idea, but I have almost the same configuration, so I'd say 421