html - adding focus on a runtime generated input box using javascript -

hi have form dynamically generates table row on button click using javascript working fine want add focus on newly generated input box in table row can in this? here script

            <script language="javascript" type="text/javascript">                 var jj=1;                 function addrow()                 {                     //alert(jj)                     var tbl = document.getelementbyid('zimtable');                     var lastrow = tbl.rows.length;                     var iteration = lastrow - 1;                     var row = tbl.insertrow(lastrow);                      var firstcell = row.insertcell(0);                     var el = document.createelement('input');                     el.type = 'text';                     el.name = 'zimname_' + jj;                     el.id = 'zimname_' + jj;                     el.size = 40;                     el.maxlength = 40;                     firstcell.appendchild(el);                        var secondcell = row.insertcell(1);                     var el2 = document.createelement('input');                     el2.type = 'text';                     el2.name = 'zimmob_' + jj;                     el2.id = 'zimmob_' + jj;                     el2.size = 10;                     el2.maxlength = 10;                     secondcell.appendchild(el2);                      var thirdcell = row.insertcell(2);                     var element4 = document.createelement("select");                     element4.name ='zim_'+jj;                     var option1 = document.createelement("option");                     option1.value='trusty';                     option1.innerhtml='trusty';                     element4.appendchild(option1);                      var option2 = document.createelement("option");                     option2.value='muqami hazrat';                     option2.innerhtml='muqami hazrat';                                   element4.appendchild(option2);                      var option3 = document.createelement("option");                     option3.value='masjidwar jamaat ka saathi';                     option3.innerhtml='masjidwar jamaat ka saathi';                                  element4.appendchild(option3);                      thirdcell.appendchild(element4);                      var fourthcell = row.insertcell(3);                     var el3 = document.createelement('input');                     el3.type = 'text';                     el3.name = 'zemail_' + jj;                     el3.id = 'zemail_' + jj;                     el3.size = 40;                     el3.maxlength = 40;                     fourthcell.appendchild(el3);                      firstcell.focus();                      // alert(i);                     jj++;                      makhtab.hh.value=jj;                     //  alert(jj);                 }             </script> 

i want add focus on first input box in generated table row

change line:

firstcell.focus(); 

to:

el.focus();