Czy aby na pewno to zmieniłeś. Zajrzałem w Twój kod i wygląda na to, że go nie zamieniłeś. Jak go zamienisz, będzie działać w 100%.
.blocker {
position: fixed;
top: 0;
right: 0;
bottom: 0;
left: 0;
width: 100%;
height: 100%;
overflow: auto;
z-index: 9999;
padding: 20px;
box-sizing: border-box;
background-color: rgb(0,0,0);
background-color: rgba(0,0,0,0.75);
text-align: center;
}
.blocker:before{
content: "";
display: inline-block;
height: 100%;
vertical-align: middle;
margin-right: -0.05em;
}
.blocker.behind {
background-color: transparent;
}
.modal {
width: 400px;
text-align: left;
background: #fff;
display: inline-block;
vertical-align: middle;
position: absolute;
top: 50%;
left: 50%;
z-index: 2;
-webkit-box-sizing: border-box;
-moz-box-sizing: border-box;
box-sizing: border-box;
-webkit-border-radius: 8px;
-moz-border-radius: 8px;
-o-border-radius: 8px;
-ms-border-radius: 8px;
border-radius: 8px;
-webkit-box-shadow: 0 0 10px #000;
-moz-box-shadow: 0 0 10px #000;
-o-box-shadow: 0 0 10px #000;
-ms-box-shadow: 0 0 10px #000;
box-shadow: 0 0 10px #000;
transform: translateX(-50%) translateY(-50%);
}
.modal a.close-modal {
position: absolute;
top: -12.5px;
right: -12.5px;
display: block;
width: 30px;
height: 30px;
text-indent: -9999px;
background: url(images/close.png) no-repeat 0 0;
}
.modal-spinner {
display: none;
width: 64px;
height: 64px;
position: fixed;
top: 50%;
left: 50%;
margin-right: -32px;
margin-top: -32px;
background: url(images/spinner_big.gif) no-repeat center center;
-webkit-border-radius: 8px;
-moz-border-radius: 8px;
-o-border-radius: 8px;
-ms-border-radius: 8px;
border-radius: 8px;
}