addEvent(window, 'load', linkPreview);

function addEvent(obj, evType, fn){
	if (obj.addEventListener){
		obj.addEventListener(evType, fn, false);
		return true;
	}
	else if (obj.attachEvent){
		var r = obj.attachEvent("on"+evType, fn);
		return r;
	}
	else {
		return false;
	}
}
function linkPreview(){
	var links = document.getElementsByTagName("a");
	for (i=0; i<links.length; i++){
		var currentLink = links[i];
		var	images = currentLink.getElementsByTagName("img");
		if (images.length == 0){
			var linkHref = currentLink.href;
			if (linkHref.match(/amazon.com/)){
				append(currentLink, "amazon");
			}
			else{
				checkLinks(linkHref, currentLink)
			}
		}
	}
}
function checkLinks(linkHref, currentLink){
	var linkHrefParts = linkHref.split(".");
	var extension = linkHrefParts[linkHrefParts.length - 1];
	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;
}