ciao grazie.
ho incluso la lib jquery.js e modificato il codice ma ancora non funziona
mi dici dove sbaglio?

Codice PHP:

<!DOCTYPE HTML PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html>
  <head>
  <meta http-equiv="content-type" content="text/html; charset=windows-1250">
  <meta name="generator" content="PSPad editor, [url]www.pspad.com[/url]">
  <title></title>

    <script type="text/javascript" src="http://jqueryrotate.googlecode.com/svn/trunk/jQueryRotate.js"></script>
    <script type="text/javascript" src="jquery.js"></script>
    


    <script type="text/javascript"> 

      newangle = 0;
      jQuery(document).ready(function($) {
    
            
            $('input').click(function() {
                if ($(this).attr('class') == "minus")
                    operation = "-";
                else
                    operation = "+";
                
                alert(operation);
                var angle = next(operation);
                $("#image").rotate(angle);
            });
        });
        
        function next(oper) {
           if (oper == "+")
              newangle += 90;
            else
              newangle -= 90;
            
           if (newangle >= 360) newangle = 0;
            
            return newangle;
        
        }


    </script>
 

    <style type="text/css"> 
        #image{
          margin:100px 100px;
        }
    </style>
 

  </head>

  <body>

        [img]https://www.google.com/images/srpr/logo3w.png[/img]
        
        <input type="button" value="+ angle" class="plus" /> 
        <input type="button" value="- angle" class="minus" /> 

        


            [url="http://jsfiddle.net/jKYkT/"]Link dell'esempio funzionante trovato in rete[/url]
        </p>

  </body>
</html>