css - Make overlay fixed-like, but the content container scrollable -

my code creates overlay blocks page black, , there's form inside of inner container. when it's active, blocks page, overlay absolute , stretches window width , height 100%, when scroll down, overlay not stretching.

when make fixed, stays in 1 place, content of not scrollable.

how make fixed, scrollable?

.quote_overlay, .email_overlay {     display: none;     position: absolute;     width: 100%;     height: 100%;     z-index: 1000;     top: 0;     left: 0;     background-image: url(img/overlay_bg.png); }  .quote_container, .email_container {     width: calc(100% - 20px);     max-width: 600px;     background-color: #ccc;     position: relative;     top: 50%;     left: 50%;     -ms-transform: translate(-50%, -50%);     -webkit-transform: translate(-50%, -50%);     transform: translate(-50%, -50%);     padding: 10px;     border-radius: 6px;     border: 0; } 

you need separate overlay element , email container. this.

your html:

<div class="email_container"></div> <div class="email_overlay"></div> 

then on css:

.email_overlay {   position: fixed;   width: 100%;   height: 100%;   top: 0;   left: 0;   background-image: url(img/overlay_bg.png);   z-index: 1; }  .email_container {   width: calc(100% - 20px);   max-width: 600px;   background-color: #ccc;   position: absolute;   top: 50%;   left: 50%;   -ms-transform: translate(-50%, -50%);   -webkit-transform: translate(-50%, -50%);   transform: translate(-50%, -50%);   padding: 10px;   border-radius: 6px;   border: 0;   z-index: 2; 

}