[squarepirate]

I google that and this was my third result.

http://www.gcflearnfree.org/internetsafety/6/print

Topic 6 talks about it. So simple.

[austinjp]

I suspect the OP is asking why bank websites do not gracefully handle the back button and prevent the errors mentioned on that page.

[wodenokoto]

Except that you don't get charged twice on Amazon or basically any web merchant when using the back button.

[mcv]

You won't get charged twice on any well-written site, but I'm still careful with the back button around any transaction.

It's not really an issue at either of my banks, because a transaction is a lot more than merely submitting a form, and requires authorization with a single-use code. But webshops tend to have far more linear transactions, and I don't always fully trust them to use the back button the way I think it should work.