How to style the input
Even the size of the input will not respond to the likes of:
<input type="file" style="width:200px">
Instead you will need to use the size attribute:
<input type="file" size="60" />
For any styling more sophisticated than that (e.g. changing the look of the browse button) you will need to look at the tricksy approach of overlaying a styled button and input box on top of the native file input. The article already mentioned by rm at www.quirksmode.org/dom/inputfile.html is the best one I've seen.