I have created a custom object(ExtranetSF) using the standard flow( Go to objects-->Create an object-->Create fields and page layout and stuff)
Then I am trying to access that custom object from my visualforce controller. The following piece of code gives me error.It says that "Field is not writeable".

My question is how do i get past this problem??? Any help

ExtranetSF__c co = new ExtranetSF__c();
co.Name = data.getNonUniqueName();
co.Extranet_Name = data.getDomainName();
co.URL=data.getUrl();
insert co;