Something

      <table width='100%' height="100%" border="0" cellspacing="1" bgcolor="#ff9933" bordercolor="#FF0000">
 
              <tr>

               <td width="70%">
 
                     <div id="div_chat" style="height: 300px; width: 100%; overflow: auto; background-color: #FFFFFF; border: 1px solid #555555;" align="left" vertical-allign="bottom"  ></div>

              </td>

              <td width="30%" valign="top">online: <br /><?php echo $_SESSION['username']; ?>

              </td>

             </tr>

             <tr>

              <td colspan="2">

                     <form action=#>
                     <input name="txt_message" type="text" id="txt_message" style="width: 350px;" />

                     <input type="submit" name="btn_send_chat" id="btn_send_chat" value="Send" onSubmit="javascript:sendChatText();return false"/>
                    </form>

              </td>

             </tr>

      </table>