1. Opacity 50% In the image:

Rules CSS Code is:

img{
opacity:.50;
filter:alpha(opacity=50);
filter: "alpha(opacity=50)";
}

2. Opacity 100% on images up to a maximum rate no transparency

The CSS Code is:

img{
opacity:1;
filter:alpha(opacity=100);
filter: "alpha(opacity=100)";
}

3. Opacity effects of 100% to 40% for status hover

The CSS Code is:

a:hover img{
opacity:.40;
filter:alpha(opacity=40);
filter: "alpha(opacity=40)";
}

4. Opacity effects of 40% to 100% for status hover

The CSS Code is:

a img{
opacity:.40;
filter:alpha(opacity=40);
filter: "alpha(opacity=40)";
}
a:hover img{
opacity:1;
filter:alpha(opacity=100);
filter: "alpha(opacity=100)";
}

5. The difference between normal text and text with opacity 60% 60%:

The CSS Code is:

opacity:.60;
filter:alpha(opacity=60);
filter: "alpha(opacity=60)";
}

Result:

Css property opacity 100

Css property opacity 60

Note: For browsers older versions still use the '-moz-opacity'.