<html>
<head>
<style>
#span{
position:fixed;
}
</style>
<meta http-equiv="Content-Type" content="text/html; charset=windows-1251">
</head>
<body><b>
<span id='span' contenteditable='true'>LOOOOOOOOOOL</span></b>
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if (e.keyCode == 45){
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span.innerHTML = 'Текст';
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</body>
</html>