image opacity is reset to zero after few seconds

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ASP.NET

Javascript

HTML

jQuery

dears,
i am trying to add image auto slider to a user control that is used in many pages
useing the code below, and every thing is ok and the image slider works normally but after a few second or minutes the slider will stop, i tried to debug i notice that the opacity is equal to zero and when i change it in it while debugging it will continue for other second and reset to zero. i tried to set it explicitly to 100 as shown in the code below but also it back to zero after few seconds

what is the problem and why the opacity is reset to zero

var imgs = '';
       $(function () {
           var cnt = imgs.length;
           var $imageSlide = $('img[id$=imageSlide]');
           $imageSlide.attr('src', imgs[cnt - 1]);
           $imageSlide[0].style.opacity = 100;
           setInterval(Slider, 5000);
           function Slider() {
               $imageSlide.fadeOut("slow", function () {
                   $(this).attr('src', imgs[(imgs.length++) % cnt]).fadeIn("slow");
               });
           }
       });

<img id="imageSlide"  runat="server" style="opacity: 100" height="200" width="750" />