Button generating code altering addresses I was playing with the website:

http://embedbitcoin.com/

to generate a payment button for my website. It asks for your bitcoin address, but when you click "Send Bitcoin" from the generated button, the address it outputs for the user is different than the one originally input.

That seems fishy, and I don't currently have any BTC to test that it is what it says it is.

If each address is unique, it is my understanding that it can't be linked to a single account, and therefore no other addresses could be generated from it, and this seems like a scam to send money to someone else's account. 

Is this understanding correct? Is this a scam?
Looks like scam yeah. It looks like they are asking for one normal bitcoin address, so any address they generate will NOT be yours.

However it would be possible to do such a thing if they would ask for the xpub seed of your HD wallet. Even then though it wouldn't make sense to trust a service like that.

Stay away!