I have found that the best way to learn anything is by doing it. Therefore, I suggest you find some web projects in the open market, friends, family, etc, and learn by doing. Chances are your skills in HTML and PHP will be the most useful. This will force you to learn CSS and Javascript. After about a solid year you should have a firm foundation of how to make something useful, and understand what the market is asking for. By then you can branch out into more PHP or make the switch to ASP.NET. .NET is great, but not ideal for small projects that are on the cheap. I wouldn't recommend focusing on XML either. Good luck on your journey.