html table colgroup

colは横 rowは縦

 <colgroup>
  <col span="1" style="width:50px; background-color:#ccccff;">
  <col span="1" style="width:100px; background-color:#ffcccc;">
  <col span="2" style="width:150px; background-color:#ccffcc;">
 </colgroup>

 <colgroup span="1" style="width:50px; background-color:#ccccff;">
 </colgroup>
 <colgroup>
  <col span="1" style="width:100px; background-color:#ffcccc;">
  <col span="2" style="width:150px; background-color:#ccffcc;">
 </colgroup>

は同じ。