I am using Firefox 47.0 under Linux Mint 17.3 (Rosa).

However, DrByte hit the hammer on the nail with the head: Some missing file suffixes in .htaccess.

One of the things I tried, on my test site, was installing the latest FontAwesome. It has a couple of extra file suffixes (although leaving them out did not break Zen Cart). After updating two of the .htaccess files, both the version of FontAwesome distributed in Zen Cart 1.5.5a (it looks like 4.5.0) and the latest (4.6.3) worked fine — so I also updated the live site.

DrByte: I did indicate my feelings were a personal bias. Standards can be a supporting argument for using technology in a certain way, but that does not mean all standards are good standards, or in some cases even a true standard (hence some of the jokes about standards). Some standards seem to be an impediment to innovation.

My statement about using fonts seeming like a kludge was partly based on my original reactions to both “ASCII Art” (and its ANSI counterpoint) and the line-drawing characters we used to see on character-only terminals. The line-drawing characters were a work-around for the hardware of the time. VisiCalc on my home-made clone of an Apple ][ used it effectively, if I remember correctly. Current hardware and software is capable of drawing vector-graphic image files without resorting to embedding images in font files.

Again, as I said, a personal bias. The biases get worse, I fear, as I get older. I even get nostalgic for programming in Assembler language

Now, back to bashing my head against the wall with Sanitizer