The browser tab is blank, and unless I'm doing something wrong there is no Favicon set for Lemmy.World. I would hazard a guess that most of us have lots and lots of tabs open at any given time. Would it be possible to add an icon to help make it easier to locate lemmy.world tabs?
You can check the Network tab in the Developer Tools, this is the image I'm getting served as favicon: https://lemmy.world/pictrs/image/66ca36df-4ada-47b3-9169-01870d8fb0ac.png
If something is bloking it it should say it in the Transferred column. I had to tweak some addons to make it work.
I'm the person who reported that. As a temporary workaround I'm using the Favicon Switcher extension (with a smaller file). You have to do it per Firefox instance; the settings aren't synced.
I suspect you have it cached and it was of a proper size before, hence your cache supplies a usable size. While the current version on the server is way too big and hence does not get rendered if loaded.