<script type="text/javascript">  
       function slide(obj, direction, a) {  
        clearInterval(window.z);  
        counter = 0;  
        z = setInterval(function () {  
         if (a ? parseInt(obj.style.marginTop) < 0 : parseInt(obj.style.marginTop) > -300) {  
          obj.style.marginTop = parseInt(obj.style.marginTop) + direction;  
          counter++;  
         } else {  
          clearInterval(z);  
         }  
        },  
        10);  
       }

  <div id="x" style="width: 100%; height: 300px; border-bottom: 5px dashed #eee; background: #555; position: absolute; margin-top: -300px;">  
        <span style="color: white; font-weight: bold;">  
            Slide Panel by $USERNAME$  
         <br />  
            Кстати, на чистом JS, без jQuery <img rel="usm" src="http://megasoft.3dn.ru/emoticons/Sypsena.gif" border="0" align="absmiddle" alt=":)">  
         <br />  
            Хотя кого это волнует.  
        </span>  
       </div>

  <div id="x" style="width: 300px; height: 50%; border-right: 5px dashed #eee; background: #555; position: absolute; margin-left: -300px; margin-top: 100px;">  
      <span style="color: white; font-weight: bold;">  
          Slide Panel by $USERNAME$  
       <br />  
          Кстати, на чистом JS, без jQuery <img rel="usm" src="http://megasoft.3dn.ru/emoticons/Sypsena.gif" border="0" align="absmiddle" alt=":)">  
       <br />  
          Хотя кого это волнует.  
      </span>  
     </div>

  <script type="text/javascript">  
     function slide(obj, direction, a) {  
      clearInterval(window.z);  
      counter = 0;  
      z = setInterval(function () {  
       if (a ? parseInt(obj.style.marginLeft) < 0 : parseInt(obj.style.marginLeft) > -300) {  
        obj.style.marginLeft = parseInt(obj.style.marginLeft) + direction;  
        counter++;  
       } else {  
        clearInterval(z);  
       }  
      },  
      10);  
     }