I found navigation group for DesktopClient in
https://msdn.microsoft.com/en-us/library/ff851994.aspx
Can any one show me its we equivalent.
There's no equivalent of these groups on the HTML client, you can only add and remove screens.
If you would like a kind of grouping functionality, I'd suggest you take a look at Michael Washington's push menu sample (http://lightswitchhelpwebsite.com/Blog/tabid/61/EntryId/3247/Visual-Studio-LightSwitch-HTML-Client-Push-Menu.aspx).