Assigning className to an input tag

Hi all,
I'd like to assign "className" to an <input> tag, but I don't manage to do that.
I tried using :
document.form1.input1.className="inputStyleName";
in order to add a certain class to all inputs in my form, for exp to:
<INPUT type="text">

I don't want to assign the className to the input in the html part, like
<INPUT class="inputStyleName" type="text">
because ns4 does not like it, (the class has properties like border and stuff).
I prefer not to write the whole form using document.write as well (regarding each browser)

I'd like that for IE and ns6.

Any suggestions?
Thanks in advance

I inserted the <style> tags only when it's not ns4,and it's working great.
And now I have this style for all the inputs in the document.

<SCRIPT language="javascript">
if (!NS4)
{document.write("<STYLE type='text/css'>");
document.write("INPUT {etc.}");
document.write("</STYLE>");
}
</SCRIPT>

So happy I found the solution myself. :-)