<style type="text/css">
#d_opacity {
background:transparent url(/content/img/css/slash_gray.png) repeat 0 0;
margin:0; padding:10px;
overflow:hidden;
}
#d_opacity div {
width:50px; height:50px;
float:left;
margin-bottom:10px;
}
</style>
<div id="d_opacity">
<!-- rgb + opacity -->
<div style="background:rgb(255, 0, 0); opacity:0.2;"></div>
<div style="background:rgb(255, 0, 0); opacity:0.4;"></div>
<div style="background:rgb(255, 0, 0); opacity:0.6;"></div>
<div style="background:rgb(255, 0, 0); opacity:0.8;"></div>
<div style="background:rgb(255, 0, 0); opacity:1;"></div>
<br style="clear:both;"/>
<!-- rgba -->
<div style="background:rgba(255, 0, 0, 0.2);"></div>
<div style="background:rgba(255, 0, 0, 0.4);"></div>
<div style="background:rgba(255, 0, 0, 0.6);"></div>
<div style="background:rgba(255, 0, 0, 0.8);"></div>
<div style="background:rgba(255, 0, 0, 1);"></div>
<br style="clear:both;"/>
<!-- rgb -->
<div style="background:rgb(243, 191, 189); "></div>
<div style="background:rgb(246, 143, 142); "></div>
<div style="background:rgb(249, 95 , 94); "></div>
<div style="background:rgb(252, 47, 47); "></div>
<div style="background:rgb(255, 0, 0); "></div>
</div>