getElementById(port) should be getElementById('port')
(quotes are needed).
Download firebug, a firefox extension. It will show you these errors.
also getElementById will not work in all browsers. If you want maximum compatibility across browsers, with the last amount of code, I'd look into a javascript framework such as jquery. Its still "regular" javascript code you're just using other people's time saving functions.
$('.port').css('cursor', 'pointer');
That would be the jquery code to set the cursor:pointer for all objects on the page with a class of "port". It would be cross browser compatible. Its also worth mentioning your example could be written more efficiently with CSS (no javascript), but I'll assume it was just an example.