Behavior of IE for ReadOnly TextArea, while hit enter key

I have one ReadOnly TextArea, some buttons, some input controls like text, radio buttons, dropdowns etc. I am taking focus to the ReadOnly TextArea and hit the enter key. As a result, the focus goes to the very first button of the page and executes its Click event. I am using Windows 7 and IE 9. It looks like IE behavior and can be handled using JavaScript.

I need a documentation link, which describes this fact. That reference is essential for our project management, to keep track, what is the actual reason to use JavaScript to handle this problem.