gamma

HTML - PHP
<div id="main">
<?php
for($i = 1; $i <= 625; $i++) {
 if($i >= 131 AND $i <= 150
  OR $i >= 156 AND $i <= 175
  OR $i >= 181 AND $i <= 200
  OR $i >= 206 AND $i <= 225
  OR $i >= 231 AND $i <= 250
  OR $i >= 256 AND $i <= 275
  OR $i >= 281 AND $i <= 300
  OR $i >= 306 AND $i <= 325
  OR $i >= 331 AND $i <= 350
  OR $i >= 356 AND $i <= 375
  OR $i >= 381 AND $i <= 400
  OR $i >= 406 AND $i <= 425
  OR $i >= 431 AND $i <= 450
  OR $i >= 456 AND $i <= 475
  OR $i >= 481 AND $i <= 500
  OR $i >= 506 AND $i <= 525
  OR $i >= 531 AND $i <= 550
  OR $i >= 556 AND $i <= 575
  OR $i >= 581 AND $i <= 600
  OR $i >= 606 AND $i <= 625
  ) {$class_white = " white";} else {$class_white = "";}
 echo "<div class=\"box".$class_white."\"></div>\n";
}
?>
</div>

CSS
#main {
 position:relative;
 width:600px;
 height:600px;
 background:#111;
 text-align:center;
}
.box {
 display:block;
 float:left;
 width:23px;
 height:23px;
 background:#172154;
 border-right:1px solid #36427F;
 border-bottom:1px solid #36427F;
}
	.box:hover {
	 border-right:1px solid #fff;
	 border-bottom:1px solid #fff;
	}
.white {
 background:#fff;
 border-right:1px solid #DAE0FF;
 border-bottom:1px solid #DAE0FF;
}
	.white:hover {
	 border-right:1px solid #111;
	 border-bottom:1px solid #111;
	}