This feature can make your Visualforce development easier by providing a view to look at the actual page and the code at the same time. Before this, the developer need to refresh the page whenever a change is made to the Visualforce page or the Apex Controller.
Below are the steps to activate the Development mode footer in your account:
- Click on your name -> Select Setup -> Click on the My Personal Information on the left panel -> Select Personal Information
- Click Edit button first -> Check the Development Mode and Show View State in Development Mode check boxes
- Click Save