Question

I am a bit confused about these two sequence of events or processes happening in conjunction to each other. Does the page handler executes first or does the somepage.aspx get execute first or do they happen simultaneously?

Answer 1

When you request a resource with a .aspx extension, the ASP.net runtime uses the default page handler to process the request. So the answer to your question is that the page handler is hit first, and then it deals with the .aspx file you requested.

Edit:

In the tutorial you link to in your comment, this is the relevant paragraph that spells this out:

Once the HTTP page handler class is
fully identified, the ASP.NET runtime
calls the handler’s ProcessRequest to
start the process. This implementation
begins by calling the method
FrameworkInitialize(), which builds
the control trees for the page. This
is a protected and virtual member of
TemplateControl class, class from
which page itself derives.

Next the processRequest() makes page
transits various phases:
initialization, loading of viewstate
and postback data, loading of page’s
user code and execution postback
server-side events. Then page enters
in render mode, the viewstate is
updated and HTML generated is sent to
the output console. Finally page is
unloaded and request is considered
completely served.

It’s the handler’s ProcessRequest method that runs the aspx page through the page lifecycle.

This MSDN page has a good description of the process, as well. See step 10 & 15 of the box that says “The request is processed by the HttpApplication pipeline.”