onmouseover不透明度变化无效

Any idea why this isn't working? The default style in CSS is opacity = 0. Not only does the opacity not change in the div I want to appear, but when the mouse goes over the link it doesn't even show it as being a link. (it works well when I use "visibility" instead of the opacity property, but it causes blinking due to the action triggering the "onmouseout" event)Any idea why this isn't working? The default st