Yes, w3schools is great for beginners. And they will check your site for errors, as well, telling you where the error is and how to fix it.
First of all you have to go through basics things of Css,HTML,php after you can develope more knowledge yourself.
I always tell people that codingforums is the greatest place to learn coding languages. html, css, php(especially), codingforums is the best for me.
i learned design html and php with books, it explains very good all steps from novice to pro, i sugest you do the same
At the moment there are a lot of sources for learning how to create websites. Apart from books there are plenty video tutorials on youtube.
W3schools is the best platform to learn web design. I have already try this site to learn web design. hope it will be helpful for you.
To learn web design you need to go to online teaching designing websites.There you can read the tutorials of designing. star of basic tools of html then go ahead step by step.