Very simple method to add custom poster frame to youtube video without using youtube API. This code is also valid in browsers not supporting window.postMessage (API uses postMessage). The trick is adding the iframe in a comment. Javascript reads comment contents and saves iframe definition to a var. When JQuery (for the sake of brevity, not real…

youtube-poster-frame.css

.video { position: relative; padding-bottom: 56.25%; /* 16:9 */ height: 0; }
.video img { position: absolute; display: block; top: 0; left: 0; width: 100%; height: 100%; z-index: 20; cursor: pointer; }
.video:after { content: ""; position: absolute; display: block; 
    background: url(play-button.png) no-repeat 0 0; 
    top: 45%; left: 45%; width: 46px; height: 36px; z-index: 30; cursor: pointer; } 
.video iframe { position: absolute; top: 0; left: 0; width: 100%; height: 100%; }

/* image poster clicked, player class added using js */
.video.player img { display: none; }
.video.player:after { display: none; }

youtube-poster-frame.html

<div class="video">
    <img src="poster.jpg">
    <!-- <iframe width="940" height="529" src="http://www.youtube.com/embed/rRoy6I4gKWU?autoplay=1" frameborder="0" allowfullscreen></iframe>-->
</div>

youtube-poster-frame.js

$(function() { 
    var videos  = $(".video");

        videos.on("click", function(){
            var elm = $(this),
                conts   = elm.contents(),
                le      = conts.length,
                ifr     = null;

            for(var i = 0; i<le; i++){
              if(conts[i].nodeType == 8) ifr = conts[i].textContent;
            }

            elm.addClass("player").html(ifr);
            elm.off("click");
        });
});

hi sorry to disturb you guys, but where do I put the script? just before the div from the video ?

Works perfectly, and makes pages with a bunch of videos load fast. Thanks!