CSS3

<DIV style="border:1px solid black; width:200px; height:200px;
 background:cross-fade(src(Com/Ahiru.png), src(Com/Picture.jpg),20%);
">テスト
</DIV>

¶

<DIV style="border:1px solid black; width:200px; height:200px;
 background:cross-fade(src(Com/Ahiru.png) 20%, src(Com/Picture.jpg));
">テスト
</DIV>

¶