http://jsfiddle.net/derekstory/vH4DV/19/
Instead of:
.ac-container input:checked ~ article{
height: 140px;
-webkit-transition: all linear .25s;
-moz-transition: all linear .25s;
-o-transition: all linear .25s;
-ms-transition: all linear .25s;
transition: all linear .25s;
opacity:1;
}
Be more specific for your transitions.
.ac-container input:checked ~ .how{
height: 140px;
-webkit-transition: all linear .25s;
-moz-transition: all linear .25s;
-o-transition: all linear .25s;
-ms-transition: all linear .25s;
transition: all linear .25s;
transition-delay: .3s;
-webkit-transition-delay: .3s;
opacity:1;
}
.ac-container input:checked ~ .About{
height: 140px;
-webkit-transition: all linear .25s;
-moz-transition: all linear .25s;
-o-transition: all linear .25s;
-ms-transition: all linear .25s;
transition: all linear .25s;
opacity:1;
}
.ac-container input:checked ~ .references{
height: 140px;
-webkit-transition: all linear .25s;
-moz-transition: all linear .25s;
-o-transition: all linear .25s;
-ms-transition: all linear .25s;
transition: all linear .25s;
opacity:1;
transition-delay: .6s;
-webkit-transition-delay: .6s;
}
.ac-container input:checked ~ .contact{
height: 140px;
-webkit-transition: all linear .25s;
-moz-transition: all linear .25s;
-o-transition: all linear .25s;
-ms-transition: all linear .25s;
transition: all linear .25s;
opacity:1;
transition-delay: .9s;
-webkit-transition-delay: .9s;
}