
HTML <!DOCTYPE> Declaration
	<!DOCTYPE html>	HTML 5 declaration
		The <!DOCTYPE> declaration must be the very first thing in your HTML document, before the <html> tag.
		The <!DOCTYPE> declaration is not an HTML tag; it is an instruction to the web browser about what version of HTML the page is written in.
		Tip: Always add the <!DOCTYPE> declaration to your HTML documents, so that the browser knows what type of document to expect.

HTML <head> Tag	<head>	The <head> element is a container for all the head elements. Tip: Put the <base> tag as the first element inside the <head> element, so that other elements in the head section uses the information from the <base> element.
	<base>	The <base> tag specifies the base URL/target for all relative URLs in a document.
	<title>Title of the document</title>	The <head> element can include a title for the document, scripts, styles, meta information, and more.
	<style>	The <style> tag is used to define style information for an HTML document. Each HTML document can contain multiple <style> tags.
	<link>	The <link> tag defines a link between a document and an external resource. The <link> tag is used to link to external style sheets.
	<meta>
	<script>	The <script> tag is used to define a client-side script (JavaScript).
	<noscript>
	</head>


HTML <meta> Tag	<meta>	Metadata is data (information) about data.
		The <meta> tag provides metadata about the HTML document. Metadata will not be displayed on the page, but will be machine parsable.
		Meta elements are typically used to specify page description, keywords, author of the document, last modified, and other metadata.
		The metadata can be used by browsers (how to display content or reload page), search engines (keywords), or other web services.
		Note: <meta> tags always go inside the <head> element.
		Note: Metadata is always passed as name/value pairs.
		Note: The content attribute MUST be defined if the name or the http-equiv attribute is defined. If none of these are defined, the content attribute CANNOT be defined.
		HTML 4.01: <meta http-equiv="content-type" content="text/html; charset=UTF-8">
		HTML5: <meta charset="UTF-8">

	<meta name="keywords" content="HTML, CSS, XML, XHTML, JavaScript">	Define keywords for search engines
	<meta name="description" content="Free Web tutorials on HTML and CSS">	Define a description of your web page
	<meta name="author" content="Hege Refsnes">	Define the author of a page
	<meta http-equiv="refresh" content="30"	Refresh document every 30 seconds
	<meta charset="GB18030">


HTML <link> Tag	<link>	The <link> tag defines a link between a document and an external resource.
	<head>	The <link> tag is used to link to external style sheets.
	<link rel="stylesheet" type="text/css" href="theme.css">	The <link> element is an empty element, it contains attributes only.
	</head>	This element goes only in the head section, but it can appear any number of times.





<script>
	<p id="demo"></p>	The <script> tag is used to define a client-side script (JavaScript).
	<script>	The <script> element either contains scripting statements, or it points to an external script file through the src attribute.
	document.getElementById("demo").innerHTML = "Hello JavaScript!";	Common uses for JavaScript are image manipulation, form validation, and dynamic changes of content.
	</script>	his JavaScript example writes "Hello JavaScript!" into an HTML element with id="demo"

	<p>JavaScript can change the content of an HTML element:</p>
	<button type="button" onclick="myFunction()">Click Me!</button>	JavaScript can change HTML content
	<p id="demo">This is a demonstration.</p>
	<script>
	function myFunction() {
	document.getElementById("demo").innerHTML = "Hello JavaScript!";
	}
	</script>

	<p id="demo">JavaScript can change the style of an HTML element.</p>
	<script>	JavaScript can change HTML styles
	function myFunction() {
	document.getElementById("demo").style.fontSize = "25px";
	document.getElementById("demo").style.color = "red";
	}
	</script>

	<script>
	function light(sw) {	JavaScript can change HTML attributes
	var pic;
	if (sw == 0) {
	pic = "pic_bulboff.gif"
	} else {
	pic = "pic_bulbon.gif"
	}
	document.getElementById('myImage').src = pic;
	}
	</script>
	<img id="myImage" src="pic_bulboff.gif" width="100" height="180">
	<p>
	<button type="button" onclick="light(1)">Light On</button>
	<button type="button" onclick="light(0)">Light Off</button>
	</p>

<noscript> Tag	<script>
	document.getElementById("demo").innerHTML = "Hello JavaScript!";
	</script>
	<noscript>Sorry, your browser does not support JavaScript!</noscript>
	<p>A browser without support for JavaScript will show the text written inside the noscript element.</p>	The <noscript> tag is used to provide an alternate content for users that have disabled scripts in their browser or have a browser that doesn't support client-side scripts