ExecuteOrDelayUntilScriptLoaded(yourFunction, 'sp.js');
       
            function yourFunction() 
    		{ 
    
          var options = { url: 'https://mywebsite.sharepoint.com/MyApp/Pages/Default.aspx', title: 'Policy', width: 900, height: 400,dialogReturnValueCallback: onPopUpCloseCallBack };
    							   SP.UI.ModalDialog.showModalDialog(options);
    
                                                        
             }
                    
             function onPopUpCloseCallBack(result, returnValue) 
    		 {
    			 if(result== SP.UI.DialogResult.OK)
    			 {
    
    				  SP.UI.Status.removeAllStatus(true);
    				  var sId = SP.UI.Status.addStatus("you clicked ok");
    				  SP.UI.Status.setStatusPriColor(sId, 'green');
    			 }
    			else if(result== SP.UI.DialogResult.cancel)
    			 {
    				 SP.UI.Status.removeAllStatus(true);
    				 var sId = SP.UI.Status.addStatus("you clicked cancel");
    				 SP.UI.Status.setStatusPriColor(sId, 'yellow');
    			 }
            }

I have used the above code to display a page named **Default.aspx** in a modal popup but unfortunately it gives me following error

![enter image description here][1]


  [1]: https://i.sstatic.net/ZKUUP.png

Is what i am doing correct? Or its not possible to display a page in modal popup in sharepoint Online? 

The same code works perfectly on sharepoint 2013 on premise.

Can anyone help?

Thanks.