IE9 equivalent of querySelectorAll

Question

I haven\'t had any problems in FF or Chrome, but IE9 chucks an error on this method. I thought I would be able to use it, due to it having been shown to be supported here:

Answer 1

This has nothing to do with quirks vs. standards mode, as the other answers suggest.

It has to do with so-called "Compatibility Mode." IE9 through IE11 use "Compatibility Mode" with intranet sites by default, and with other sites according to your settings.

To tell IE that your site actually uses web standards and it shouldn't hobble itself, either:

1. Update your server config to send the X-UA-Compatible header with the value IE=Edge, or

2. Add it as a meta tag right at the top of your head element markup:

Of course, you should have a doctype as well, but just a doctype won't deal with the (in)Compatibility Mode issue.