You have finished reading a c++ book? Great.
Now, read the rfc for tcp, ip, udp, dns, ftp and http, followed by the dtd for html, sgml, xml and xhtml. And then we can move on to the typography and layout logic courses followed by reading full the css specification.
Oh, and you want to take some classes in graphics formats, how to load them and how to display them. Especially how to display them. There is a lot of work for how to display stuff, how to load it, how to manage it and how to draw custom graphics.
And this leads to the gui toolkit leasons, you will need advanced skills in gui design, with focus on the toolkit that you are going to use.
Oh, and somewhere on the line, you will have to learn how to write a javascript engine and how to allow existing plugins to work with your application.