function linkPreview(){
	var links = document.getElementsByTagName("a");
	for (i=0; i<links.length; i++){
		var currentLink = links[i];
		var images = currentLink.getElementsByTagName("img");
	 	// Check if the link is an image. We don't want icons next to images.
		if (images.length == 0){
			var linkHref = currentLink.href;
			// Find all links directed to amazon.com 
			if (linkHref.match(/amazon.co/)){
				append(currentLink, "amazon");
			}
			else{
				checkLinks(linkHref, currentLink);
			}
		}
	}
}

function checkLinks(linkHref,currentLink){
	var linkHrefParts = linkHref.split(".");
	// extension is the last element in the LinkSplit array
	var extension = linkHrefParts[linkHrefParts.length - 1];
	// In some browsers there is a "/" placed after the link. removes the "/"
	extension = extension.replace("/","");
	if( extension in { doc:1, pdf:1, ppt:1, txt:1, xls:1, zip:1 } ){
		append(currentLink,extension);
	}
}

function append(currentLink,extension){
	var span = document.createElement('span');
	span.innerHTML = "&nbsp;";
	currentLink.parentNode.insertBefore(span,currentLink.nextSibling);
	span.className = extension;
}

addEvent(window,'load',linkPreview);