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HTML

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HTML preprocessors can make writing HTML more powerful or convenient. For instance, Markdown is designed to be easier to write and read for text documents and you could write a loop in Pug.

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Adding Classes

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About the <head>

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Insecure Resource

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CSS

About CSS Preprocessors

CSS preprocessors help make authoring CSS easier. All of them offer things like variables and mixins to provide convenient abstractions.

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CSS Base

About CSS Base

It's a common practice to apply CSS to a page that styles elements such that they are consistent across all browsers. We offer two of the most popular choices: normalize.css and a reset. Or, choose Neither and nothing will be applied.

Vendor Prefixing

About Vendor Prefixing

To get the best cross-browser support, it is a common practice to apply vendor prefixes to CSS properties and values that require them to work. For instance -webkit- or -moz-.

We offer two popular choices: Autoprefixer (which processes your CSS server-side) and -prefix-free (which applies prefixes via a script, client-side).

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JavaScript

About JavaScript Preprocessors

JavaScript preprocessors can help make authoring JavaScript easier and more convenient.

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Babel includes JSX processing.

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You can apply a script from anywhere on the web to your Pen. Just put a URL to it here and we'll add it, in the order you have them, before the JavaScript in the Pen itself.

If the script you link to has the file extension of a preprocessor, we'll attempt to process it before applying.

You can also link to another Pen here, and we'll pull the JavaScript from that Pen and include it. If it's using a matching preprocessor, we'll combine the code before preprocessing, so you can use the linked Pen as a true dependency.

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Packages

Add Packages

Search for and use JavaScript packages from npm here. By selecting a package, an import statement will be added to the top of the JavaScript editor for this package.

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Using packages here is powered by esm.sh, which makes packages from npm not only available on a CDN, but prepares them for native JavaScript ESM usage.

All packages are different, so refer to their docs for how they work.

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HTML 

              
                <div id="header">Scroll Down</div>
<div id="main">
	<div id="container"></div>
  Keep Going!
</div>
<div id="footer">You Made It!</div>
!

CSS 

              
                  body{
    border:0;
    font-family:arial;
    font-size:50px;
    line-height:500px;  
    margin:0 auto;
    padding:0;
    text-align:center;
    width:960px;
  }
  #header{
    background:#faa;
    height:500px;
  }
  #footer{
    background:#aaf;
    height:500px;
  }
  #main{
    background:#afa;
    height: 1800px;
    line-height:1800px;
    position: relative;
  }
    #container{
       background: none repeat scroll 0 0 orange;
       height: 200px;
       position: absolute;
       right: 10px;
       top: 10px;
       width: 200px;
    }
!

JS 

              
                jQuery(document).ready(function($){
	//variables
	var $window = $(window);
	var $container = $("#container");
	var $main = $("#main");
	var window_min = 0;
	var window_max = 0;
	var threshold_offset = 50;
	/*
	 set the container's maximum and minimum limits as well as movement thresholds
	*/
	function set_limits(){
		//max and min container movements
		var max_move = $main.offset().top + $main.height() - $container.height() - 2*parseInt($container.css("top") );
		var min_move = $main.offset().top;
		//save them
		$container.attr("data-min", min_move).attr("data-max",max_move);
		//window thresholds so the movement isn't called when its not needed!
		//you may wish to adjust the freshhold offset
		window_min = min_move - threshold_offset;
		window_max = max_move + $container.height() + threshold_offset;
	}
	//sets the limits for the first load
	set_limits();
	
	function window_scroll(){
		//if the window is within the threshold, begin movements
		if( $window.scrollTop() >= window_min && $window.scrollTop() < window_max ){
			//reset the limits (optional)
			set_limits();
			//move the container
			container_move();
		}
	}
	$window.bind("scroll", window_scroll);
	
	/**
	 * Handles moving the container if needed.
	**/
	function container_move(){
		var wst = $window.scrollTop();
		//if the window scroll is within the min and max (the container will be "sticky";
		if( wst >= $container.attr("data-min") && wst <= $container.attr("data-max") ){
			//work out the margin offset
			var margin_top = $window.scrollTop() - $container.attr("data-min");
			//margin it down!
			$container.css("margin-top", margin_top);
		//if the window scroll is below the minimum 
		}else if( wst <= $container.attr("data-min") ){
			//fix the container to the top.
			$container.css("margin-top",0);
		//if the window scroll is above the maximum 
		}else if( wst > $container.attr("data-max") ){
			//fix the container to the top
			$container.css("margin-top", $container.attr("data-max")-$container.attr("data-min")+"px" );
		}
	}
	//do one container move on load
	container_move();
});
!
999px

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