div.main_contents {
  float: left;
  width: 740px;
  
}

div.main_contents img {
  margin-bottom: 0;
}

div.main_contents_body {
  background: url(../images/common/sub_main_bg.gif) top center repeat-y;
  width: 740px;
  margin-top: 0;
}

div.main_contents_body img.explanation01 {
  margin-bottom: 50px;
}

div.main_contents_body img.str01 {
  margin-top: 100px;
  margin-bottom: 100px;
}

div.main_contents_foot {
  margin-bottom: 50px;
}