How to change iframe inner text?

I'm using a web browser to login to site and submit articles its very simple but at some places when there is iframe instead of textarea it 开发者_如何学运维gets very complicated.At some times just putting valye in the textarea automatically puts value in the iframe and sometime it doesn't ,So is there any way that can be applied at all iframes to change their innertext.

Thankyou

If the main page and the iframe are on

• same domain, browers allows you to access iframe's DOM
• different domain, web browsers do not allow you to access and change DOM for security concerns.