Simple way to get element by id within a div tag?

Question

Please forgive me if I repeat the question.

I have HTML　that all elements inside a div tag has different id, suppose I have already get the reference to the div, is

Answer 1

Unfortunately this is invalid HTML. An ID has to be unique in the whole HTML file.

When you use Javascript's document.getElementById() it depends on the browser, which element it will return, mostly it's the first with a given ID.

You will have no other chance as to re-assign your IDs, or alternatively using the class attribute.