I suspect you'll get dozens of different answers to this question. My own advice would be to start with basics of HTML and CSS. Get on top of that before you venture into programming languages, databases, etc. But that's just my opinion, for what it's worth.
But it's also worth asking why you want to learn web design. If it's because you like acquiring new skills, or you enjoy the challenge of something new, or because you fancy the idea of creating your own sites .... in all those cases, I would encourage you to give it a try, and wish you the best of luck.
But if your reason is that you hope to get a job as a web designer, or perhaps set up your own web design company, then I would advise you to be cautious. It's a competitive field, and if you are starting from absolute zero ... well, to be brutally frank, it could be a long hard road to success.