Actually, you can. Companies require this stuff all the time. If you're going to use HTML5 and CSS3, you're not going to be able to use IE9.

This is the same excuse that was used that kept IE6 around so long. Do you anticipate supporting a several years old version of Chrome or FireFox?

>I think my IE9 did work with Bootstrap.. and then (just yesterday) stopped working. Must be something has changed. As far IE11, I have to make my project work on many browsers.. I can't tell the customer(s) that they have to upgrade to IE 11 in order to use my application.
>Thank you for the link. I will check it out.