Is there any path assignment can be used by skin.css ?

Just likes <%= SkinPath %> can be converted to the skin path in the asc file.

Is there any token can convert to the skin path or else(portal root, etc...) and can be used in the container.css or skin.css?

CSS files do not get processed by ASP.Net, they get sent directly from IIS, so it is not possible to have server side code in the CSS file (unless you map it in IIS).

The good news is you don't need it.  Every path from a CSS file is relative from where the CSS file is.

So if your CSS file is in the Skin Folder, then you are already there. If you want to reference a background image that is in a folder under the skin folder you can do it like this in the CSS file:

.MyClass {
background:url(images/myimge.gif);
}

I don't know what this means.  Can you give me an example?