Firefox -moz-placeholder, not working - css

Question

I can't get this placeholder to style correctly in Firefox 13.0.1
I have an input field with a placeholder:
<input class="textFieldLarge" placeholder="Username" id="username" name="username" type="text" />
I have this CSS:
.textFieldLarge{
width:400px;
height:50px;
line-height:50px;
padding-left:5px;
padding-right:5px;
background:none;
background-color:#FFF;
border:solid 1px #BBB;
font-family:Arial, Helvetica, sans-serif;
font-size:20px;
color:#333;
}
.textFieldLarge::-webkit-input-placeholder, .textFieldLarge:-moz-placeholder{
font-style:italic;
color:#BBB;
}
This should style the text field #333 and the placeholder #BBB italic. I have this working with chrome and IE but can't figure FF out.
EDIT, FOUND THE PROBLEM THAT I APPLIED ::-webkit-input-placeholder AT THE SAME TIME
Still would appreciate a fix, but I doubt possible as it works fine when both are applied separately. Not a real issue any more but a little annoying.

Answer 1

If one part of a selector is invalid, then the whole selector will be invalidated.
Therefore, one needs to have two different rules for each of -moz- and -webkit-.

Answer 2

It's been a while since posting this question, but in addtition to Gerve's answer, one should use ::-moz-placeholder for Firefox 19+: http://mzl.la/15FPlx6 and can add support for IE10 with :-ms-input-placeholder. So the final code will look like that:
.textFieldLarge::-webkit-input-placeholder {
font-style:italic;
color:#BBB;
}
.textFieldLarge:-moz-placeholder {
font-style:italic;
color:#BBB;
}
.textFieldLarge::-moz-placeholder { /* Firefox 19+ */
font-style:italic;
color:#BBB;
}
.textFieldLarge:-ms-input-placeholder { /* IE10 */
font-style:italic;
color:#BBB;
}