Text input placeholders not displaying in IE and Firefox

My text input placeholders refuse to display in IE and Firefox despite having used the -moz-placeholder attribute. This can be viewed on the contact page here if you are using Firefox or IE.

Can someone please help I have been trying to figure this out for weeks. A sample of my code is below:

 input::-moz-placeholder, textarea::-moz-placeholder {
    color: #aaa;
    font-size: 18px;
}

    input:-ms-input-placeholder, textarea::-ms-input-placeholder {
        color: #aaa;
        font-size: 18px;
    }

input::-webkit-input-placeholder, textarea::-webkit-input-placeholder {
    color: #aaa;
    font-size: 18px;
}