I am completely new to cq and i just started learning cq coupleof day back. i am trying to create a component and editing it..i sucessfully created a component but when i tried to edit in IE8 iam getting items.xtype is null..and in other browser iam getting a dialog which is blank..can someone please suggest..forgive me i miss anything here..plz suggest..
Did you check the documentation about existing xtypes in CQ AEM , http://dev.day.com/docs/en/cq/current/developing/widgets/xtypes.html
Note also that this is related to ExtJS and so it would be good that you also get documented on ExtJS how it works etc.. as it will help you more on finding the root cause.
And last check how foundation components are made, that usually give many good example of possible configuration for the dialogs.