This is a follow-up to my comments on VS launcher for F# web apps, where I can put an example of the changed markup to the F# class library project to make it act like a web project and launch a browser with your Default.aspx page when you hit F5.
First, add the highlighted element to the topmost
<PropertyGroup> clause in the .fsproj file thus:
where the first GUID is for web app, and the second for F# (as you can see by looking for the project in the solution file).
At the bottom of a C# web application .csproj you will find a block of code like
which you just want to copy and paste into your F# project following the
or equivalent line.
Now adding a trivial Default.aspx file containing
Welcome to ASP.NET on F#!
and the default web.config from a C# web project to the F# library, and running the project launches me that trivial web page into Firefox.
Actually getting F# to play nice with ASP.Net, I leave to those more versed in the latter.