Does Non-Existing Attribute (For Browser) Will Break Something?

Sub-question for HTML Placeholder browser compatibility . I need to have that effect for my inputs and textareas. At the moment, I use JScript to do that. If wo开发者_C百科uld switch to "placeholder" (HTML5 attribute)... does it break something in older browsers that don't support "placeholder"?

It would be great that if browser doesn't support it... it just ignores it. No "place-hold" text. That's all.

In the HTML, unsupported attributes are ignored.