1<script type="text/javascript"> 
2<!-- 
3    function formatText (tag) { 
4        var selectedText = document.selection.createRange().text; 
5
6        if (selectedText != "") { 
7            var newText = "[" + tag + "]" + selectedText + "[/" + tag + "]"; 
8            document.selection.createRange().text = newText; 
9        } 
10    } 
11//--> 
12</script> 
13
14<form name="my_form"> 
15    <textarea name="my_textarea"></textarea><br /> 
16    <input type="button" value="bold" onclick="formatText ('b');" /> 
17    <input type="button" value="italic" onclick="formatText ('i');" /> 
18    <input type="button" value="underline" onclick="formatText ('u');" /> 
19</form>