Page_init
This event is the first event to occur when an ASP.net page is executed,
this is the event where you should be performing any initialization steps
that you need to setup or create instances of server controls.
Its generally advised not to access controls in this event as there is no
guarantee of the controls been created at this stage, its in this event the
controls are actually created.
This event fires only the first time the page is loaded and from the next
time on a postback Page_init is not fired.
Page_load
This is the event where most of our work will be done, this event occurs
when all objects/controls on the page are created and will be available for
use.
Unlike Page_init, this event is loaded everytime when the page is postback.
