[Gavin]

So I've decided that the time is ripe to start using PNG 24 alpha transparency.

In the past it was impossible because of IE, then moved up to simply being a major hassle. So for me PNG24 was shelved.

Now IE7 can handle it and it is now already 40% of the market, and IE <= 6 is now less than 36% ( According to WIKIpedia anyway) and it should drop quickly.

Also there are some newer scripts that can force legacy IE to use filters to handle PNGs. This has been around for a while but the newer ones are much easy to implement wide scale, unlike the image by image coding of yore.

The one I found that seems to fit the trick is iepngfix.htc
find it here IE PNG Fix - TwinHelix

You drop one line into a style sheet- that's it. If browser is IE it will look over all graphics and if it's a PNG it will deal with it.

So the question is what is the downside?
Any probs using it?
Will non-IE browsers choke on it?
Is this going to crash slower windows boxes?

I haven't seen any problems in safari or firefox, but I have seen evidence of overhead on slower PCs. I've noticed that it loads the pics incorrectly at first then they kind of flash a second later when the filter kicks in. Is this a deal killer for anyone?

[Ozmodiar]

I don't know of any problems, per se, but I use a different method.

[Madrag]

on slower machines, it does take more time to load!
in some cases, the iepngfix.htc method requires you to specify the width and height of the image, and doesn't work well with backgrounds positioned on the right!
I've had some cases where this solution works in a version of IE6 and not in other versions
(I can't recall which versions, sorry).

I usually only use this solution if really desperate!
Otherwise, try to use an alternative for the png in IE6 (and use the png for any other browser).
I designed a website which used gif with a full background only for IE6, and the other browsers would "see" a non-uniform background and transparent png on top
Search the "_" and "*" CSS hacks!

as for the other browsers, it simply won't be used, and from my experience, neither IE7, Safari2, FF2 (mac/PC) will suffer from this hack

[NosferatusCoffin]

Originally Posted by Madrag 

I've had some cases where this solution works in a version of IE6 and not in other versions.

The problem you are most likely having is a bug that is unique to IE7.

IE7 has problems with rendering the proper height of floated elements. For example, if you have a sidebar that is floated left and you use a background image for it, in most cases it will not render properly. Usually by cutting off the image at a certain point.

The fix for this is to use the "min-height" property and apply that as a height for the floated element.

Example:
#sidebar {
width: 200px;
min-height: 610px;
margin: 0;
padding: 0;
float: left;
background: url(img/image.png) no-repeat;
}

You can go over to Austin Matzo's blog for more information on this bug.