If you are using gmail on google chrome then you faces problem of bad request error 400 .
if you are try accessing gmail on a different browser like Firebox , chrome and etc.
i will try to solve your problems related to Gmail 400 error. This article is about how to fix 400 bad request error on gmail .
I faced this problem currently when I was sending a sample of gift card that got through Gift Card Spread promo code to my friend using Gmail. If this article found helpful to me I will be very thankful to you.