CSS rules with url shouldn't be allowed

[AdamWr]

I guess it's related to - #1293 and to this - #659
As far as I understand, using url in CSS rules (#$#) should be blocked and rule like this shouldn't work and it doesn't work:

example.org#$#body { background: lightblue url("https://www.w3schools.com/cssref/img_tree.gif"); }

but if we change url to for example URL or uRl then rule works fine 🙃:

example.org#$#body { background: lightblue URL("https://www.w3schools.com/cssref/img_tree.gif"); }

Link - https://example.org/

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