Your best solution is to look at the "opacity" tag of an element.
For example:
.image
{
opacity:0.4;
filter:alpha(opacity=40); /* For IE8 and earlier */
}
So in your case it should look something like :
<html><span style="opacity: 0.5;"><font color=\"black\" face=\"arial\" size=\"4\">THIS IS MY TEXT</font></html>
However don't forget the tag isn't supported in HTML5.
You should use a CSS too :)