Ok, copy/paste this exact code into a php-file:
<table>
<tr><td>
<p>This is your information:</p>
</td></tr>
<tr><td>Browser and OS version:</td> <td> <? echo $HTTP_USER_AGENT ?></td></tr>
<tr><td>IP address:</td> <td><? echo $REMOTE_ADDR ?> </td></tr>
<tr><td>Screen resolution:</td> <td><script language="JavaScript">
document.write(window.screen.width +"x"+ window.screen.height) </script></td></tr>
</table>
Gives you both IP, OS and browser version and Screen size.
Good luck.