function createFlashMarkup(width,height,uri,replaceid){

 var obj = document.createElement('object');
 obj.setAttribute('type','application/x-shockwave-flash');
 obj.setAttribute('width',width);
 obj.setAttribute('height',height);
 obj.setAttribute('data',uri);

 var p_m = document.createElement('param');
 p_m.setAttribute('name','movie');
 p_m.setAttribute('value',uri);

 obj.appendChild(p_m);

 var div = document.getElementById(replaceid);
 document.getElementsByTagName('body')[0].replaceChild(obj,div); 
}

window.onload = function(){
 createFlashMarkup('550','400','vuurwerk.swf','replaced-by-flash');
}