“Property transition doesn't exist” error

Question

I am having issue when validating my CSS with the W3C validator http://www.css-validator.org/ . It gives me the following error:

Property transition doesn't exist : 0.5s ease 0.5s ease

Here is my HTML code:

<div class="class_name">test</div>

Here is my CSS code

.class_name{
    width:100%;
    float:left;
    transition: 0.5s ease;
    -webkit-transition: 0.5s ease;
    -moz-transition: 0.5s ease;
    -ms-transition: 0.5s ease;
    -o-transition: 0.5s ease;
}

HTML works in all browsers and I am not sure what is wrong with the code. Is this a W3C validator bug or I am doing something wrong?

Answer 1

The site you used does not appear to be legitimate or officially endorsed by W3C — although it looks similar, there is a lot of garbage at the bottom (including a widget for a Facebook page that does not even remotely seem official) and there are slight layout differences.

The official Jigsaw W3C CSS Validator, which does not appear to be the same one you used, validates your CSS just fine. For reference, the official URL is http://jigsaw.w3.org/css-validator .