How can i store data client side without uaing server in html/js

By only using HTML and js you wont be able to store something on a client's machine due the lack of permissions. To get a clients username you can store the data like you said on the server in a session or you can store at the client by using cookies. But with cookies you have to be careful since someone can steal or craft them which is a security issue

i will learn php i guess XD...

You don't have to learn php for a server language for eg. ruby or python will do as well but I guess to get a feeling php is the easiest and fastest to start with ^^ Good luck haha

i just whant to code a favoris bar that remever your favorit web site as a chrome extwnsion server still seme like overkill XD

Oh Chrome extensions have their own way of saving client stuff... As far as I know this is even possible with js only... Check out the chrome extension API and play around a little bit