Is a cancel button necessary in a web form?

1. What is the purpose of Cancel button?
2. Should cancel be a button or a link?

What is the purpose of Cancel button?

In this article

A cancel button is clicked whenever the user presses the ESC key, regardless of which other control on the form has the focus. Such a button is usually programmed to enable the user to quickly exit an operation without committing to any action.

Should cancel be a button or a link?

To summarize

The cancel option is similar to aborting an action, and therefore similar to navigating back to the previous state of the UI. Navigation is represented in web UI as hyperlinks, and thus the cancel option should be a hyperlink.