Video automatically download when open using iframe in popup

Question

i want to display video in popup. so i have used iframe for that. but when i open popup it automatically download video rather then open it in popup. below is my popup code

<div id="Portfolio_div" class="white_content_loading animate SlideInDown"  style="display:none;"> 
  <div class="port-wrap-img">
    <a href="javascript:void(0)" class="close"></a> 
    <div class="lg-bt1">
    <span id="Prev"  style="pointer:cursor;"  class="previous port-pr"></span>
    </div>

    <div id="divedit1" class="setmar2" align="center" >

    <div style="clear:both;"></div>
    </div>
    <div class="lg-bt2">
      <span id="Next" style="pointer:cursor;" style="" class="next port-ne"></span>
    </div>
  </div>  

<div style="clear:both;"> &nbsp; </div>
</div>
<div id="fade_share1_div" class="black_overlay" style="display:none;"></div>

And below is my script which load video to popup

firstvideo=site_url.ajaxurl+data;
        var imgStr='<iframe src='+site_url.ajaxurl+data+' width="500px" height="290px" id="you_vid" />  ';

        $('#Portfolio_div').css('display','block');
        $('#fade_share1_div').css('display','block');
        $('#divedit1').html(imgStr);

I don't know what is the problem please help me to get out of this