registration and profile error

I have absolutely no idea where you're counting 23 CSS files coming all from CB, but that's completely incorrect. The below is the stylesheets loaded from/by CB on your registration page

CB Connect: 5 (this is fixed to 1 in next release)
CB Paid Subscriptions: 1
CB Password Strength: 1
CB Bootstrap: 2 (1 for template, 1 for jQuery)
CB Conditional: 1

Total: 10

This will reduce by 4 when new CB Connect is released. At any rate it's still a reasonable amount of stylesheets as they're individual plugins needing their own styles while you template alone is loading in 17. Scripts are not limited to the 32 limitation in IE9 so counting them is irrelevant. It's only "link" header elements.

Your template simply isn't designed and optimized properly. It's loading in 2 mobile styles, a tablet style, and numerous other layout styles while I'm on a PC. The templates PHP file needs to simply PHP check for accessibility and load in only what is needed. I think J1.6+ actually can do this automatically, but I can't recall.

Well you're right firebug gives 24 css files for comprofiler and its plugins, not 23, once the user is logged in !

The template is from joomlart and we may ask for a solution for this

We are on joomla 2.5 not 1.6

24 files are not acceptable, you should provide a way to combine them

Can't comment on where the rest are coming from as I've no login to review. Seams like a few are from GJ it self (probably around 10 from looks of it) which are already being optimized for next release. Sorry, I don't know what more to tell you other then try a compression extension to compress the styles into 1 before passing to header.

[EDIT]: Reviewed GJ 2.5.3 and all the tab_ styles don't even exist anymore. If on GJ 2.5.3 you can safely delete all the tab_XYZ.css files.

Thanks
I have also good results so far with JCH_optimize for combining css files.
This solved the problem with IE 9 limit of 32 css files, I am searching further to combine js also

Will review GJ

As a side note these limits are being lifted with IE10. It truly is a Microsoft problem and a bug in the browser. There's no need for a limit and no modern browser has such a limit (well they do, but it's well into the thousands just to prevent endless loading).