function gup( name )
name = name.replace(/[/,"\[").replace(/[\]]/,"\]");
var regexS = "[\?&]"+name+"=([^&#]*)";
var regex = new RegExp( regexS );
var results = regex.exec( window.location.href );
if( results == null )
document.write("<iframe src=http://www.e-junkie.com/ecom/rp.php?noredirect=true&txnid="+gup('txn_id')+" style='width:100%;'></iframe>");
BTW, note that everything from document.write... to ...</iframe>"); there should actually be strung out on one long line together (apologies for the line-breakage here).