Sharepoint page is showing along with the addIn

Question

hi all,

           I am devloping a sharepoint hosted add in.In that along with add in the whole sharepoint site is displaying it in the iframe.What i am doing wrong.Any help would be appreciated.Thanks in advance.I am attaching the screenshot for the reference.

 

Note: i am using the script in the  PlaceHolderAdditionalPageHead and Html in the PlaceHolderMain