The <!DOCTYPE> declaration helps the browser to display a web page correctly. There are different document types on the web. To display a document correctly, the browser must know both type and version. The doctype declaration is not case sensitive. All cases are acceptable:
<!DOCTYPE html> <!DOCTYPE HTML> <!doctype html> <!Doctype Html>
<!DOCTYPE HTML> has to be the first line, followed by <html>
CSS is used to define styles for your web pages, including the design, layout and variations in display for different devices and screen sizes.
HTML was NEVER intended to contain tags for formatting a web page. HTML was created to describe the content of a web page, like: <h1>This is a heading</h1> <p>This is a paragraph.</p> When tags like <font>, and color attributes were added to the HTML 3.2 specification, it started a nightmare for web developers. Development of large web sites, where fonts and color information were added to every single page, became a long and expensive process. To solve this problem, the World Wide Web Consortium (W3C) created CSS. CSS was created to specify the document's style, not its content. In HTML 4.0, and later, all formatting should be removed from the HTML page, and stored in separate CSS files.
The style definitions are normally saved in external .css files. With an external style sheet file, you can change the look of an entire Web site by changing just one file!
First we will explore the internal method. This way you are simply placing the CSS code within the <head></head> tags of each (X)HTML file you want to style with the CSS. The format for this is shown in the example below.
<head> <title><title> <style type="text/css"> CSS Content Goes Here </style> </head> <body>
With this method each (X)HTML file contains the CSS code needed to style the page. Meaning that any changes you want to make to one page, will have to be made to all. This method can be good if you need to style only one page, or if you want different pages to have varying styles.