yes, FLAC streaming might be experimental, but the OP did ask for lossless.
I just checked an encoder I use for online broadcasting and it does have the OGG FLAC option. I never noticed it before but it's there.. so maybe this really is a viable option for lossless..
However, as for the OP's needs.. I think he wants an on-demand thing which will play back a specific file in the browser.. so.. I think the best answer for the OP at this moment is to create 2 files for each of his demos.
You would create two versions of the same file:
1 - OGG at 320kbps (or 256kbps)
1 - AAC at 320kbps. (or 256kbps)
The reason why you want OGG and AAC of the same demo is because not all browsers natively support both formats. Here is a list of the browser differences.
Internet Explorer 9.0+: .mp3, .aac
Chrome: .ogg, .mp3, .wav, .aac*
Firefox: .ogg, .wav
Safari: .mp3, .aac, .wav
Opera: .ogg, .wav
So, then after you create your two files you can embed them into your web page like this..
<source src="demo.aac" type="audio/mp4">
<source src="demo.ogg" type="audio/ogg">
Your browser does not support the audio element.
The above code will fail-gracefully and play the file that the browser supports. If the browser supports neither, it will show the message "Your browser does not support the audio element".