what is wrong with this

what is wrong with this

Not able to replace this text with a word highlighted:

  1.     $('p *',$('iframe').contents()).each(function(){
    $('*',this).contents().add($(this).contents()).filter(function(){
    return this.nodeType==3; 
    }).each(function(){
    var html=this.text();
    html.replace(/subject/g,'<span style=backgroundcolor:yellow>subject<\span/>');
    $(this).replaceWith(html);
    })
    });