No offense, but what do you mean by "[you] know quite a bit of c++?"
As you should know, C++ must be compiled before it can execute. C++ compilers, ultimately compile the source code (C++) into machine code (binary information), or something directly executable by the target OS. How would you propose to take a native executable meant for a particular hardware configuration, and run it on a webpage, on multiple and likely differently configured machines?
I suppose another route might be to compile your C++ code into something more portable, but C++ isn't designed for that. It makes some assumptions that would make this difficult. Perhaps you want a syntactically similar, but fundamentally different language, something like Java...?
I did google your question and surprisingly Google Chrome has Native Client @.@