问题
A bunch of sites mention support in IE9, but I assume this was something that appeared in the Betas, or RC. It doesn't appear to be supported in IE9 final. Can someone confirm this?
回答1:
No, placeholder text for form elements was never implemented for IE9. It is easily (and commonly) done with JavaScript.
Placeholder support was added in IE10.
来源：https://stackoverflow.com/questions/5329175/does-ie9-rtw-support-the-placeholder-attribute-on-input-elements