var height = 740;
var html_to_write = '<iframe id="widget_gospodarka" scrolling="no" frameborder="0" height="' + height + '" marginheight="0" marginwidth="0" noresize="noresize" width="250" src="http://gadzet-gieldowy.gazeta.pl/index.php?c[0]=SGN&c[1]=MCI&c[2]=IPX&c[3]=VIC&c[4]=SGR&c[5]=PKO&c[6]=WAS&c[7]=LBW"></iframe>';
document.write(html_to_write);
var iframe = document.getElementById('widget_gospodarka');
iframe.src = iframe.src;