Knowledge about CSS Alpha transparency. Please see the following code:
Program code
filter:alpha(opacity=50); /* IE */
-moz-opacity:0.5; /* Moz + FF */
opacity: 0.5; /* Browsers that support CSS3 (FF 1.5 also supports it)*/
A brief explanation, IE uses the private property filter:alpha(opacity), Moz Family uses the private property -moz-opacity, and the standard property is opacity (CSS 3, Moz Family partially supports CSS3). The following value is transparency, using percentage or decimal (alpha(opacity)) to use values greater than 0 and less than 100, which is actually a percentage). From the above code you don't see Opera. Yes, Opera does not support standard opacity, nor does it have its private properties that can support Alpha transparent. However, we know that Opera supports Alpha transparent PNG images (of course Moz Family also supports it). So we can use background images to achieve the Alpha transparent effect.
The key is:
Program code
background:transparent url(alpha80.png) left top repeat!important;
background:#ccc;
filter:alpha(opacity=50);
Since Moz Family supports Alpha transparent PNG, there is no need to use its private properties. Of course, you can use standard opacity, but don't use Alpha transparent pictures and opacity at the same time, as this will become a mixture of the two. You can download the above example and then check the comments for /*opacity:.5;*/.