I have a Master page and a webpage that uses the Master page.
In both I have a Page_Load event handler.
In which order are the Page_Load>
The content page load event will fire before the master page load event.
See here for full order (MSDN: Events in ASP.NET Master and Content Pages)
Copying incase link goes dead:
The following is the sequence in which events occur when a master page is merged with a content page: