When an Opportunity Owner is creating a New Opportunity, if they press the “Enter” key, the user will receive the following message “Do you want to save this Opportunity?” with buttons for “Yes” and “No”.
 

• If the user selects “Yes” and all required fields have been completed, the opportunity will save and the opportunity owner will be taken to the newly created Opportunity Record.
• If the user selects “Yes” before all required fields have been completed, the opportunity owner will receive the normal errors that state certain fields are required.
• If the user selects “No”, the user will be taken to the “Opportunities” section.

issue:
While creating a New Opportunity, if user is pressing the “Enter” key, then the record is not getting save. Afer clicked on ENTER its redirecting to the opportunity list view page.
My expectation:
After all data entry in the new opportunity VF page if user click on ENTER button then the data should save and details page should open.
What is the issue on the VF page? Why ENTER button not working?