Eğer siteme kullanıcı basın (oturum). (Giriş blok) gizli ve değiştirin olacak (bloğu işareti)

bu yüzden biraz yardıma ihtiyacım var ben oturumu ile yapılan bu iradeyi biliyorum ama ben bunu yapamam .....

                                     <div class="sidebar">

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                               <!-- Begin Sign in block  -->


         <div class="art-Block">
                            <div class="art-Block-tl"></div>
                            <div class="art-Block-tr"></div>
                            <div class="art-Block-bl"></div>
                            <div class="art-Block-br"></div>
                            <div class="art-Block-tc"></div>
                            <div class="art-Block-bc"></div>
                            <div class="art-Block-cl"></div>
                            <div class="art-Block-cr"></div>
                            <div class="art-Block-cc"></div>
                            <div class="art-Block-body">
                                           <div class="art-BlockHeader">
                                            <div class="l"></div>
                                            <div class="r"></div>
                                            <div class="art-header-tag-icon">
                                             <div class="t">Sign in</div>
                                             </div>
                                             </div><div class="art-BlockContent">
                                             <div class="art-BlockContent-body">





  <form action="login.php" method="post" >
  <table width="171" border="0" >
  <tr>
    <td width="97">
    <input class="put" name="uname"  type="text" size="10" />    </td>
    <td width="64" align="right" class="text_un">User Name</td>
  </tr>
  <tr>
    <td>
    <input  type="password" size="10" name="password" /></td>
    <td align="right" class="text_pw">Pass Word</td>
  </tr>
  <tr>
    <td>&nbsp;</td>
    <td align="right" valign="top"><input class="button" type="submit" name="button" id="button" value="Sign in " /></td>
  </tr>

  </table>
  </form>




                                  </div>
                                  </div>
                                  </div>
                                  </div>


                            <!-- End Sign in block -->

<!-- ---------------------------------------------------------------------------------------- -->


                           <!-- Begin Sign Out Block  -->

         <div class="art-Block">
                            <div class="art-Block-tl"></div>
                            <div class="art-Block-tr"></div>
                            <div class="art-Block-bl"></div>
                            <div class="art-Block-br"></div>
                            <div class="art-Block-tc"></div>
                            <div class="art-Block-bc"></div>
                            <div class="art-Block-cl"></div>
                            <div class="art-Block-cr"></div>
                            <div class="art-Block-cc"></div>
                            <div class="art-Block-body">
                                           <div class="art-BlockHeader">
                                            <div class="l"></div>
                                            <div class="r"></div>
                                            <div class="art-header-tag-icon">
                                             <div class="t">Sign out </div>
                                             </div>
                                             </div><div class="art-BlockContent">
                                             <div class="art-BlockContent-body">





  <form action="login.php" method="post" >
  <table width="171" border="0" >

  <tr>
    <td>&nbsp;</td>
    <td align="right" valign="top"><input class="button" type="submit" name="button" id="button" value="Sign Out " /></td>
  </tr>

  </table>
  </form>





                                  </div>
                                  </div>
                                  </div>
                                  </div>

                            <!-- End Sign Out Block  -->

                                  </div>
                                  </div>