Beware of the
Yes, it is an SVG image 😀
It seems that Firefox and Internet Explorer have a problem with raw SVG code as image source. I had to URL encode it (base64 would have worked too, but it is about 30% bigger and gzips worse).
Dear Mozilla and Microsoft programmers:
It is legit and standard conform to use the raw stuff. “The Real Opera(TM)” (aka <14) can do that since version 7 (or may be even earlier), Chrome since about version 7 (that is several years later than Opera 7), and Vivaldi since the beginning too. Fix it!