I have created one custom object called Site, and I have created a lookup from Opportunity to that Custom object. Now I can see the opportunity related list in my custom object, there one button called New Opportunity also available. My client wanted me to change the button name and put the Visual force page which I created for Custom object inside that one. I can't change the standard button so I have gone to the Custom button option. I have created a custom button and given the type as List Button and content source as URL and inside the button I have written the below statement. As expected, I can call the visual force page to that button. But the only issue I can not call the custom object field values inside the visual force page. In the below statement I have referred the Visual force page and custom object fields. Please guide me in this issue.