Development Javascript help

Probably me being blind and missing something obvious, but I just can't get this function to work.
It's supposed to show or hide elements, or change their opacity depending on the variables given to it.

Code:

//Shows or hides elements
function display(elementid,show,fade,opacity)
{
	switch(show)
	{
		case 1:
			if(fade=1)
			{
				document.getElementById(elementid).style.display = "inline";								
				
				//Standard
				document.getElementById(elementid).style.opacity = opacity / 100;
				
				//IE Legacy                  
				document.getElementById(elementid).style.filter  = "alpha(opacity="+opacity+")"; 
			}
			else
			{
				document.getElementById(elementid).style.display = "inline";
			}
			break;
		
		case 0:
			{
				document.getElementById(elementid).style.display = "none";
			}
			break;
	}				
}

So for example if I run the function

Code:

display('foo',1,1,40);

It should change the element

Code:

<span id="foo">bar</span>

To 40% opacity. Except..... it doesn't.

Any ideas?

 

No one?!

 

works fine here...

The problem might actually be the way you're including the script in the page. Post some of the HTML as well?