Question: How do you test for whether a div has opacity = 0?

I have tried:

```
if (jQuery("#slideshow div#prev").css({opacity: 0})) 
    {
jQuery("#slideshow div#prev").animate({opacity: 1.0}, 500); 
    }

```

but it seems to fire off the animation even when the opacity is already 1.0?

Answer: 
Use `css('opacity')`:

```
if (!jQuery("#slideshow div#prev").css('opacity')) {
    jQuery("#slideshow div#prev").animate({opacity: 1.0}, 500); 
}

```

This code checks if the return value of `.css('opacity')` is falsy, if it is, then either the CSS hasn't been set or the value itself is falsy, in which case you *would* want to proceed and run the `animate` call.
Correct syntax would be

```
if (!jQuery("#slideshow div#prev").css('opacity')) 
    {
       jQuery("#slideshow div#prev").animate({opacity: 1.0}, 500); 
    }

```

css('opacity') would return 0 and if() condition will be become true.