I have the following iframe tag:
I created this a long time ago, so things may have changed with HTML5. Two questions:

1. I cannot find the #view=fit in any searched. The # would seem to indicate a name tag in the document, so that doesn't make sense, but if I change it = ?view=fit, none of the other parameters work. Also, the scrolling=no tag attribute (not in my iframe) is deprecated, so how would I remove the scrollbar? I see no official attribute for this. The only way I can make the scrollbar disappear is to create a sufficiently long iframe.

2. The toolbar=0 works on Edge

Sounds like an pdf-specific extension. See this: https://stackoverflow.com/questions/...n-embedded-pdf

Other browsers support the toolbar=0, but not Firefox. There is a rather elaborate way of allegedly doing so using a userContent.css: https://support.mozilla.org/en-US/questions/1119523, but I'm not willing to go to that extreme. Perhaps one day Firefox will fix this.

Nevertheless that doesn't really answer my question about the #view=fit, nor why #view works but ?view does not. I thought the "#" is normally a reference to an internal name tag, but apparently not for pdfs. Perhaps I just copied this noop from someone's example once-upon-a-time and it never did anything.

You might have missed this bit: this is a pdf-specific extension, which has nothing to do with standard meaning of character # in html