What is the behavior of a Web browser when it receives an invalid element?

The behavior of a Web browser when it receives an invalid element depends on the browser that you use to browse your application.
Most of the browsers ignore the invalid element; whereas, some of them display the invalid elements on the page.

Except Chrome, which fix its best possibility, all other MOSTLY ignore it.
You can use W3C validator http://validator.w3.org/

Well, Firefox ignores the invalid element but Internet explorer pops up an error message.
But this is not always a case as with xml issue firefox just shows the first line with error heading.
Most of the time it happens with xml or client side code(javascript, DOM, jquery)

it will be canceled (treated as not exist)