figured it out. needed to set the "width" attribute - which i was lacking. so now the code should look like this:

.textbox {
margin: 10px 200px 10px 10px;
width: 450;
padding: 10px;
border: 2px solid white;
background: #333333;
filter: alpha(opacity=75);
-moz-opacity: 75%
}

again, props to erica for the tip in the first place. it was spawned from her query of "hey, how do you do the transparency on your textbox" to which i answered that it was in fact a hack that used a transparent gif. knowing that there was another way she did a quick search and found some info from solar dream studios and passed it along. cheers!