[css] CSS3 Transition not working

I couldn't get transitions to work on this page, anybody has any idea why?

div.sicon a {
    transition: background 0.5s linear;
    -moz-transition: background 0.5s linear; /* Firefox 4 */
    -webkit-transition: background 0.5s linear; /* Safari and Chrome */
    -o-transition: background 0.5s linear; /* Opera */
    -ms-transition: background 0.5s linear; /* Explorer 10 */
}

For me, it was having display: none;

#spinner-success-text {
    display: none;
    transition: all 1s ease-in;
}

#spinner-success-text.show {
    display: block;
}

Removing it, and using opacity instead, fixed the issue.

#spinner-success-text {
    opacity: 0;
    transition: all 1s ease-in;
}

#spinner-success-text.show {
    opacity: 1;
}

HTML:

<div class="foo">
    /* whatever is required */
</div>

CSS:

.foo {
    top: 0;
    transition: top ease 0.5s;
}

.foo:hover{
    top: -10px;
}

This is just a basic transition to ease the div tag up by 10px when it is hovered on. The transition property's values can be edited along with the class.hover properties to determine how the transition works.

If you have a <script> tag anywhere on your page (even in the HTML, even if it is an empty tag with a src), then a transition must be activated by some event (it won't fire automatically when the page loads).

A general answer for a general question... Transitions can't animate properties that are auto. If you have a transition not working, check that the starting value of the property is explicitly set. (For example, to make a node collapse, when it's height is auto and must stay that way, put the transition on max-height instead. Give max-height a sensible initial value, then transition it to 0)