I want to be an expertise in html 5.can any body inform me about some platform of learning html 5

I highly recommend that you consider the following online resources, in the order provided :

http://www.codecademy.com - a great resource for absolute beginners.
https://dash.generalassemb.ly/ - after CodeCademy, you'll be ready for these tutorials
http://www.codeavengers.com - even more exercises!

In my experience, I've found people progress through HTML5 very well after mastering the basics on CodeCademy, and moving forward from there. Anytime that you get stuck, there's a whole Daniweb community to help you out!

Good luck - learning HTML5 is a lot of fun, it gets hard here and there, but with a bit of patience and effort, you'll quickly become an expert.

inform me about some platform of learning html 5

What do you mean by platform? You can think of HTML5 as a standard. HTML is simply markup and if you develop HTML5 pages, you are following rules and guidelines.

To become an expert, I would recommend getting a hold of a few books, visiting the W3C and looking at their documentation http://www.w3.org/html/wg/drafts/html/CR/, and just developing, testing, etc... You only need a browser to work with HTML5 pages. No web server is needed. No special IDE is needed either. It can all be done with a simple text editor.

I think the OP asked about a learning platform for HTML5, not what kind of platform HTML5 is.

Yes, that makes more sense. thanks for clarifying that.

I live in a country with 11 different languages, you learn to read between the lines :)