I think i have solved the problem:
var document = document.contentDocument;
var doc_bodies = document.getElementsByTagName('a');
var link_count = doc_bodies.length;
var i = 0;
do{
if(doc_bodies[i].href.match('example')) {
var doc_body = doc_bodies[i];
var url_div = document.createElement("iframe");
url_div.scrolling = "no";
url_div.marginWidth = 0;
url_div.marginHeight = 0;
url_div.frameBorder = 1;
url_div.style.cssText = "width:400px;height:200px;border-radius:5px;left:0px;-moz-box-shadow: 10px 19px 20px #7b8674; /* firefox */ box-shadow: 10px 19px 20px #7b8674;margin-bottom:10px";
url_div.id = 'added-by-firefox-extension';
url_div.src = doc_bodies[i].href;
doc_bodies[i].parentNode.replaceChild(url_div, doc_bodies[i]);
}
else
{
i++;
}
}while( i < doc_bodies.length);
Now i have to include this in a Firefox Addon. If anyone could help, that would be great. Thanks