Having posted a small test file to the stix comment page , I noticed that the stix site has a larger test file (choose "STIX Font Glyph Tables" from the menu options on the STIX site, which will take you to
This differs from my test (apart from being rather larger) in that each cell is individually assigned an appropriate font with separate CSS classes rather than having a single CSS font list and relying on the font choice to fall through fonts that do not have the appropriate glyph. The results are different but still a bit disappointing.Three images of my Windows XP setup, one of the Font directory just to show they are there, one of the top of the allGlyphs file showing side by side in Firefox 126.96.36.199, Opera 9.21 and IE 7.0.5730.11, note that only FF actually shows the bold and italic variants. then the same three browsers showing the bottom of the file. here FF is all white, Opera is white for some characters and two missing glyph markers for others, and IE is mainly white but strangely enough actually renders the last few entries, which are monospace digits.
The images link to larger screen dumps which show (or rather do not show) the glyphs more clearly.