Mine

function showTableBorders(){

if(document.all){
    var tablesIframe = window.frames['article_rEdit'].document.all.table;
    var tdIframe = window.frames['article_rEdit'].document.all.table.td;         
}
    else{
      var tablesIframe=document.getElementById('article_rEdit').contentDocument.getElementsByTagName('table');
      var tdIframe = document.getElementById('article_rEdit').contentDocument.getElementsByTagName('td');	
}

   
    for (var n = 0; n < tablesIframe.length; n++) {
            //tablesIframe[n].className = 'tableIframe';
            tablesIframe[n].className='tableIframe';;
    }

    for (var n = 0; n < tdIframe.length; n++) {                            
            tdIframe[n].className = 'tdIframe';
    }

}