.p_close {
    float:right; width:15px; height:14px; margin:11px 10px 0 0;
    background:url(../img/popup_close.png);
  }
  .p_body {
    background:#000; left:0; top:0; position:fixed; width:100%; height:100%; opacity:0.4;
      -moz-transition:opacity 800ms;
      -o-transition:opacity 800ms;
      -webkit-transition:opacity 800ms;
    transition:opacity 800ms;
  }


/* js стили — декларативно */
.js__popup {}
  .js__p_start {}
  .js__p_close {}
  .js__p_body {}
  .js__slide_top { height:0; overflow:hidden; top:0; }
  .js__fadeout { height:0; overflow:hidden; opacity:0; }