I'd like to start using question marks at the end of clauses as well as sentences. To indicate this I would like to use a question mark with a comma underneath, which I'd like to call a quomma.

There doesn't seem to be a Unicode code point for this unconventional punctuation, so what is the most Web-f开发者_如何学Pythonriendly way of doing this?

• The combining diacritical mark doesn't seem to work anywhere I've tried it: ?̦ (Though is there something which prevents overlappingʔ̦ because the glottal stop mark, which looks almost like a dotless question mark (ʔ) does seem to work, as you just saw!)
• SVG support is not widespread, and this would require a per-font SVG anyway.
• A raster image seems a bit of a crap solution.
• Is there some cheeky but not-too-hacky HTML/CSS?
• Any other ideas?

Have a look at the combining diatrics (charts), in particular U+0326 (COMBINING COMMA BELOW).

The HTML ʔ̦ produces:

ʔ̦

Since this is unlikely to be a grapheme used in any existing language, whether that works or not on your browser may depend on a number of factors related to Unicode and font support.

This one works inline; even IE can handle inline-block displays on span-elements:

<p>Some text with a quomma in it <span class="quomma">?<span class="c">,</span></span> and some more text</p>

CSS:

span.quomma {
    display: inline-block;
    position: relative;
}

span.quomma .c {
    display: block;
    position: absolute;
    left: .1em;
    top: 0;
}

Perhaps not a satisfactory answer, but you don't need a special symbol for this.  Simply use a question mark and continue the sentence as if it were a comma:

Would you prefer some of a? is b more to your taste? or how about c?

Like, I was at the mall? and I saw this guy? and he smiled at me? and I was like OMG!
    – Mike Daniels

I'm not sure of the history or whether it was ever mainstream, but I have seen it, on occasion, used clearly.  I doubt any style manual endorses it whole-heartedly—or even at all?—but since you're up for generating your own punctuation, that doesn't seem a huge concern.  At one time, wasn't it common to indicate sentence breaks specially? or not?  Wouldn't such indication obviate the quomma? or is there still a need for it?  (Can I keep that up any longer?  Nope.)