<script language="javascript">
    var countInputs = 0;
    function dodajInput()
    {
  document.getElementById('inputLayer').innerHTML+='<br /><input name="userfile_'+countInputs+'" type="file" />';
  countInputs++;
    }
</script>

<form enctype="multipart/form-data" method="post">
<div id="inputLayer">
    <input type="hidden" name="MAX_FILE_SIZE" value="900000" />
</div>
    <input type="submit" value="Send File" />
</form>
<a href="javascript:dodajInput();">Dodaj pole formularza</a>

function addInput(id)
{
    var oDiv = document.getElementById(id);
    var oInput = document.createElement("<input type='file'>");
    oDiv.appendChild(oInput);
    return;
}

[HTML] pobierz, plaintext 
<div id='fragment'>
<a href="javascript:addInput('fragment')">Tutaj nowe inputy:</a>
 
</div>
[HTML] pobierz, plaintext 

var countInputs = 0;
function addInput(id)
{
    var oDiv = document.getElementById(id);
    var inputElement = document.createElement("input");
    inputElement.setAttribute("name","userfile_"+countInputs);
    inputElement.setAttribute("type","file");
    oDiv.appendChild(inputElement);
    countInputs++;
}

[HTML] pobierz, plaintext 
<div id="inputLayer"></div>
<a href="javascript:addInput('inputLayer')">Dodaj input</a>
[HTML] pobierz, plaintext