 <p>Since this </p> <p><code>$("#offerd_desc li").css('opacity', '0');</code></p> <p>Sets the opacity INSTANT to 0, you would use the animation();</p> <pre><code>$("#offerd_desc li").mouseover({ $(this).stop().animate({opacity:0.5},500); }); $("#offerd_desc li").mouseout({ $(this).stop().animate({opacity:0.5},500); }); </code></pre> <p>Use stop() before you do animation, else it will cause flickering when you hover it fast. and i strongly recommend to use speeds such as 200 - 500 ms, cause else animation will take to long time.</p>