Depending on your website market you also shouldn't set language based on browser preferences, but should be user selectable. I've spent years working with des

Depending on your website market you also shouldn't set language based on browser preferences, but should be user selectable. I've spent years working with desktops builds from US-based IT teams that have then been deployed globally (so language is US and paper size is letter). And then access control is added over the top to prevent end-users changing those settings because when they get it wrong it causes excessive support calls.