what does it mean < a href="javascript:;"

Hi I am looking at the following code and ttrying to understand what "  <a href="javascript:;" "
means here:

<ul>
           <li class="li"><a href="javascript:;">
             <span class="selected">  2009  </span></a><ul>
              <li class="li"><a href="javascript:;" title="2000" class="">2000</a></li>
              <li class="li"><a href="javascript:;" title="2001" class="">2001</a></li>
              <li class="li"><a href="javascript:;" title="2002" class="">2002</a></li>
              <li class="li"><a href="javascript:;" title="2003" class="">2003</a></li>
              <li class="li"><a href="javascript:;" title="2004" class="">2004</a></li>
              <li class="li"><a href="javascript:;" title="2005" class="">2005</a></li>
              <li class="li"><a href="javascript:;" title="2006" class="">2006</a></li>
              <li class="li"><a href="javascript:;" title="2007" class="selected">2007</a></li>
              <li class="li"><a href="javascript:;" title="2008" class="">2008</a></li>
              <li class="li"><a href="javascript:;" title="2009" class="">2009</a></li>
              <li class="li"><a href="javascript:;" title="2010" class="">2010</a></li>
           </ul>
             
              </li>
             </ul>