Okay, i can't provide much information because important parts (included files, functions, assets) are not present for me.
I assume that the problem is somewhere in the first lines if that file before your HTML DOCTYPE, otherwise you would get any type of output.
You can chaeck that by uncommenting that part or parts of that parts to come closer to that issue.
The charset error i get in my Firebug too is just an aftereffect of the real issue, because that "Error 204" message page doesn't provide any charset information and your responding webserver doesn't too (or gets somewhere lost at dyndns).
Would be interesting to know if you have that Error 204 issue only with dyndns or from localhost too.
Thats all i can say from far away here without a full test case.
Hope that helps you anyway