Hey! @rajesh you mean the right of the screen? I think it's usually on the right side. I don't know if there's a specific reason for that, it's just we tend to put Actions that are taking us forward in our flow to the right, and cancel and back to the left. Think of all the apps you use on your phone, you have the back and cancel actions always on the right. This is because that's how we read, from left to right. Does this answer your question?
You may have to look back into Amazon and eBay's case study for this because those websites have been running for more then 20+years and they were 1 of the few e-commerce websites that started selling online. My prediction would be since it has been working for them it became industry standard.