I've tried this and it seems to work - any reason why it's NOT a good way to do it?

<?
if (preg_match("/iP(od|hone|ad)/i", $_SERVER["HTTP_USER_AGENT"])) {
echo "iPad/iPhone";
} 
else { 
echo "Not iPad/iPhone";
} 
?>

I've read elsewhere that browser sniffing like this is a bad idea as there could be both false positives and positive falses (do they exist? haha). If I do something based on screen size, it could become very long with the iPad, iPhone5, landscape, etc, etc.

You may want to check this thread Why Do I Need A Mobile Website [webmasterworld.com]. It has some tips. You can also do a web search for open source device detection scripts.

Marshall

Div targeting Ipod... Iphone..

Put your CSS into a perl/php whatever script. Detect the device via user agent and print the right CSS, like:

If Ipod: display:block/inline/tablet, whatever suites your needs.
If not ipod: display:none;