Web page is.
Web page is Is a HTML document that is stored in web server.
On the hardware side, a web server is a computer that stores web server software and a website's component files (e.g. HTML documents, images, CSS stylesheets, and JavaScript files). ... An HTTP server is a piece of software that understands URLs (web addresses) and HTTP (the protocol your browser uses to view webpages).
Web pages are what make up the World Wide Web. These documents are written in HTML (hypertext markup language) and are translated by your Web browser. Web pages can either be static or dynamic. ... A Web site is a collection of pages. A Web page is an individual HTML document.
there are two ways, which are almost the same. then there are many others :) So, you can have what is really a text file that has the html code stored on it. The text file is saved to the server, then when its called to a web browser, it renders in a way that looks good.
SO to answer your question, it's not only all the BIG websites that make use of HTML and CSS but also all websites that exist make use of some HTML and CSS. By definition HTML, is the Hypertext Markup Language, so it's mandatory. ... They can be written in things like PHP, say, which create the HTML and CSS.