Steps to replicate the issue (include links if applicable):
- With some old browser (e.g. Firefox 68) Visit https://en.wikipedia.beta.wmflabs.org/wiki/Bert
- Hover over Bert's book
SyntaxError: '#mw-content-text a[href][title]:not(.extiw, .mw-selflink, .image, .new, .internal, .external, .mw-cite-backlink a, .oo-ui-buttonedElement-button, .ve-ce-surface a, .cancelLink a)' is not a valid selector
What should have happened instead?:
No JS error
I regularly test code with an antique browser as code that works on an old browser tends to work fine on a modern browser as well, but not the other way around. Prevents me from accidentally using features that may not be widely supported.
IIRC support for this style of CSS selector isn't quite ubiquitous yet.
browser stack: Replicable in Firefox 68 on Windows 10
QA Results - Prod