What are the differens between these 2 lines?

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 strict//EN" >
VS
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 transitional//EN" >

What does strict do that transitional doesnt??

This code works when I hav strict but not when I have transitional, why??
VB Code:
  1. <table height='150px' width='150px' border='1'>

  2.   <tr>

  3.     <td>Pelle

  4. <span id="BilockListView1" style="height:100px;width:100px;">

  5. <div style='height:100px;width:100px'>

  6. <div style='overflow: scroll;overflow-x:hidden;height:100%' id='tC'>

  7. <table ID='BilockListView1'>

  8. <tr style="top:expression(document.getElementById('tC').scrollTop);position:relative;">

  9. <td>PubId</td>

  10. <td>OrgName</td>

  11. <td>Edition</td>

  12. </tr>

  13.  
  14. <tr><td>4</td><td>654 SMO Datasheet</td><td>-99</td></tr>

  15. <tr><td>1</td><td>AvestaPolarit Stainless Steel</td><td>-00</td></tr>

  16. <tr><td>3</td><td>Machining handbook</td><td>-99</td></tr>

  17. <tr><td>2</td><td>Welding guidelines</td><td>-99</td></tr>

  18.  
  19. </table></div></div></span>

  20.     </td>

  21.     <td>Olle</td>

  22.    </tr>

  23. </table>