Firefox transitions not working

Question

This is my CSS setup:

#element1, #element2{
  -webkit-transition: left 0.3s;
  -moz-transition: left 0.3s;
  -o-transition: left 0.3s;
  transition: left 0.3s; 
}

body.open #element1, body.open #element2 {
   left: 245px; 
 }

The problem is that the transition just doesn't work in Firefox, it's fine in all other browsers.

Solution

You need to set a starting left for firefox (and now Chrome).

#element1, #element2{
    left: 0px;
    -webkit-transition: left 0.3s;
    -moz-transition: left 0.3s;
    -o-transition: left 0.3s;
    transition: left 0.3s; 
}

You're going to be better off always setting a default value for any transition. That way you can have complete control.