Anyone who references a bad programmer's work (or lack of knowledge, for that matter) in order to conclude the worth of their chosen language obviously never understood the principle of "correlation does not imply causation."
So, Goma, you can ignore those answers and comments. They are of little worth.
On to the matter at hand, @Scott Whitlock's advice is best:
I suggest learning any language that's practical, but keep an open mind.
In your question you state that you want to be "a .net developer for the web." I argue that you are selling yourself short.
Good programmers are not PHP Programmers or C# Programmers. Understanding a range of languages/tools, and more importantly, getting-things-done is far better than boxing yourself into a package like .NET Programmer.
You will likely benefit not only from the things you learn about statically typed languages (Java, C#, Pascal), but also dynamically typed languages (PHP, Python, Ruby). More important is that you learn what the difference means between the two. And that's just one example.
Understanding why your tool behaves (not how it behaves) is key to becoming a better developer.
You likely "see most freelanc[sic] developer tend to provide PHP development more than ASP.NET" because PHP has a very low entry barrier. Also, many small companies (those looking for freelance work) opt for a LAMP stack due to the cost factors associated with the alternatives.
Don't let any of that get you down. If you apply yourself, while keeping and open mind, you can stop worrying about where to start, and just start.
I recommend starting with C#, if that's your goal. You should also spin up a couple of PHP projects in your spare time so that you can compare the two.