> A good website give you the ability to move without this button.
I disagree, fairly strongly. Re-implementing behavior that the user already has in their client is at best superfluous, and at worst very confusing.
> It's like Android VS iOS. The first one has a back button, the other don't.
iOS apps implement history as part of their UI because iOS doesn't have provision for one in the default UI. This is changing, as gestures become more and more common. I don't think I've actually used a "back button" on my iPhone in months. I pretty much take its presence as communicating that it's possible to go back, not as a means to do so.
A good website don't need using this button.
And to navigate between websites, using a tab for each website is fine. Especially when comparing results from Google.