Glowball and theEclipse are both right.
This is what works for IE and NN (I only can test in IE4.0 and NN4.73)
only NN
<INPUT TYPE="submit" width="200" height="40" name="buttonNN" value="buttonvalue NN"><br>
only IE
<INPUT TYPE="submit" style="width:200px; height:40px;" name="buttonIE" value="buttonvalue IE"><br>
IE + NN
<INPUT TYPE="submit" width="200" height="40" style="width:200px; height:40px;" name="buttonIENN" value="buttonvalue IE + NN"><br>
Some other CSS properties work for IE + NN
(I don't know all so, try other properties)
<INPUT TYPE="submit" width="200" height="40" style="font-size:70%; font-style:italic; text-decoration: underline; Font-Family: times new roman; width:200px; height:40px;" name="buttonIENN2" value="buttonvalue IE + NN nr.2"><br>
Hope this helps,
Erik