What is HTML after all? Hypertext Markup Language or HTML(standardized by W3C or World Wide Web Consortium) is a browser-side language which can be interpreted by different browsers to present you all the beautiful and ugly billions of web pages out there. Basically with HTML you use a pair of tags(open tag and close tag) to present elements:<p></p> for paragraph, <h1></h1> for heading 1 etc. But there’re tags without closing tag, such as <br /> tag and <hr />tag. Like any language, HTML has its own grammar, always surrounded by <html></html>tags(the DTD(Document Type Definition) is another story), within which there’re <head></head>and <body></body> tags. Within head tags you’ll have title, meta(description, keyword), link(for CSS),script(which can also be put in body tags) tags. The main content are all located in body tags, here we’ll meet H1 through H6, p,table, div, span, ul, ol and other tags.
CSS is the short form of Cascading Style Sheets, which formats the HTML elements with different styles(be it background image, padding, margin or font size). It’s worth noting that you can format the margin or padding on four sides independently in a single line of code, it goes clockwise(namely top, right, bottom, left). CSS can be a individual .css file or embedded within the html files.
Comparing to CSS and JS, HTML is like the building blocks of a web page, it controls the structure, CSS and JS are there to make the web pages in style and improve the interactivity.