This plugin exists because IE <= 8 don't exactly handle transparency well. Things work fine on 7 and 8 until trying to fade an image with alpha transparency, then IE tries to apply both an opacity and fade filter, wreaking havoc on the image. There are fixes to this, but none work particularly well with CSS backgrounds, thus we have this, to skip the fade altogether on IE <= 8.
Essentially, this is shorthand for:
var checkIfIe = ($.browser.msie && $.browser.version.substr(0,1) < 9) ? true : false;
if(checkIfIe === true){
$(this).show(callback);
} else {
$(this).fadeIn(speed, easing, callback);
}
So you likely won't need it unless you have plenty of fades you're looking to apply it to or you just love saving 5 lines. And if you do use it, you'll negate any savings without concatenating your code to minimize HTTP requests. (Thanks to Koes for bringing this up.)
Use this just like jQuery's fadeIn and fadeOut, but appending Safe. That is:
$(selectorOrGroup).fadeInSafe(speed, easing, callback);
or
$(selectorOrGroup).fadeOutSafe(speed, easing, callback);
All three arguments are optional, and the first two will be skipped over in IE. Instead, a simple .show() or .hide() will run, then the callback will be executed.