Why does iE9 not have html5 effect_html/css_WEB-ITnose

As shown in the picture, the above picture is a screenshot in the chrome browser. When you click to log in, the form will be verified. If it is not filled in,
will pop up a prompt. I use the required attribute in HTML5 For verification. I have the same page in IE9 but
does not have such an effect. There is no pop-up message after clicking.
And I have added

Such javascript, why does IE still not work? Does IE9 not support the required attribute?
Here Please give me some advice. Thank you!~~

Reply to discussion (solution)

Add header

Try this

It doesn’t work, I have tried it before.

??JS only can correctly display the new features of html5, there are no new ones For compatibility management, you added it using

Please tell me how to add it, thank you!~~