W3schools is an very informative website about web development and also helpful for new learners as well as advanced.It provides all the necessary tools that are used in web development like HTML, CSS, PHP, JAVA SCRIPT, BOOTSTRAP and even some advanced level languages like XML and etc.The good thing about this website is, its open source means free to use and modify in any other ways.
I have been using this website since a long time to learn some basics of web development.One thing I found in it more helpful is provides all the informations chapter wise with example and it makes more easier to practice .I really love this website and would recommend to my friends if they want to learn web development go through this one.