so i've done this a few times. there are other ways of doing it but below is the way i did it.
first thing you need to do is find a microcontroler that you can controll from a PC.
i have used both PICs and AVRs, connected via their UART to a PCs serial port.
under normal circumstances this allows you to controll the microcontroler from terminal software such as hyperterminal.
next you need to install some sort of programming language on the PC that can be run as a CGI (Common Gateway Interface) which will allow you to run your program as a script from a web server.
also for that programing language you will need some libraries that let you controll the serial port.
i used Python as a programming language and ModSerial to controll the serial port because i knew Python and it's free (open source) but there are other choices.
next step, you need to install webserver software on your PC that can run CGI scripts.
i used Apache because its free and i know it well but again, there are other (probably simpler) choices.
connect your computer to the internet so it is reachable from the outside world.
you do have firewall software in place right?
design a fancy web page with buttons that link to your CGI script, in turn sending controll strings through the serial port to your micrcontroller and controlling your creation.
the individual steps i have described above are all simple enough once you know how but i think you are in for a lot of research if you choose to do it this way.