Can we use just <a href="#">
for "back to top" button at bottom of the page? I think it will work always in all browser. We do need to define any ID .
When we click on this <a href="#">
it takes to page top always. or what are other best practices to use "back to top" button.
Yes, you can and should use that, as that is what it means. There are no other practices for doing a 'back to top' button, and even if there is, they're unnecessarily complicated compared to this.