HTML 5 is still a client sided markup language. if you want to create more robust, or dynamic, web pages you will need to integrate the client side page (HTML, JS, CSS. etc) a server sided platform live .NET, Java, Grails, etc. As this is a .Net forum, I would humbly suggest .Net. You can easily do this in ASP.Net. Of course, there are always exceptions: you can "fake" dynamic content by using cookies and what not.

Anyway, which ever server sided scripting your using (you say JSP and ASP?) would handle the logging in request (presumably by validating through a db?) and would then pass the succesful data (like username) to the client side to be rendered.