problem with window.getSelection on FF and Opera

[Olbaltums]

First I’m sorry for mistakes that I will write – I know English very bad but I hope you will understand my question.

I write a simple JavaScript code:

var userSelection;
if (window.getSelection) {
userSelection = window.getSelection();
alert(userSelection + ' Mozzila, Opera');
}
else if (document.selection) { // should come last; Opera!
userSelection = document.selection.createRange();

var selectedText = userSelection;
if (userSelection.text)
selectedText = userSelection.text;

alert(selectedText + ' IE');
}

but problem is that my selected text show only Internet Explorer, but Fire Fox and Opera don’t and I don’t understand why. Can someone help me?