Encourage your users to update their browser via a simple middleware.
It looks like this:
To show the screen to anyone using IE < 9 and Opera < 10. The default mode is to only specify browsers you know you can't/won't support. Allowing for new browsers to attempt to work on the site.
adding a footer
If you want to provide a support email or other message, just add a
footer field with any valid html to be displayed at the bottom of the page.
Because if you aren't going to support a browser, the least you can do is tell your users.
Isn't this bad practice?
No. Forcing a proprietary, closed source, old, unsupported, single platform browser on people is a bad idea. Saying your site needs Chrome or Firefox to run is fine; especially if you are using new web tech not found in other browsers.
What if my users can't install a new browser?
This is highly unlikely. If they are in a corporate setting, then why are you supporting this nonsense? If they are a home user, you are doing them a favor by introducing them to a better web. If they really can't install a new browser then I guess you need to spend the countless man hours making sure your site really does work in IE 6.
How many browsers should I blacklist?
Ideally, only the ones you won't be aiming to support. Don't overuse this middleware and remember to at least support free browsers when you can!
npm install browserkthx