Can't properly set vertical-align

tags css

My problem: want to div content be in the middle of parent div.

CSS structure:

  <div class= 'sign_in'>
    <div class= 'sing_form'>
    </div>
    <div class='fb_sign'>
    </div>
    </div>

Basically it is sing-in window, on the right it is email/pass form, on the left - fb login button, and this button I want to be in the middle, but it works with top, works with bottom, on vertical-align:middle it again on the bottom.

CSS:

.sign_in {
    position: absolute;
    border-style: solid;
    border-width: 2px;
    border-color: #c1ffc6;
    background: #fff;
    padding: 2%;
    width: 30%;
    font-family: Arial, sans-serif;
    z-index: 9999999;
    font-size: 14px;


}
.sings_form{

    display: inline-block;
    border-right-style: solid;
    padding-right: 10%;
    border-width: 1px;
    border-color: #c1ffc6;

}
.fb_sing {

    display: inline-block;
    vertical-align: top;
    margin-left: 10%;


}