Javascript issue

Where do I post about javascript? Anyway, ......

[Stuperfied]

Why would this be happenning?
PS: I had to put some spaces in the tags to get them to show up.

[u r l=http://www.example.com][/u r l]
][/u r l]http://www.example.com][/u r l]
[ b ]Cat[ /b ]
[ u ]Dog[ /u ]
[ /b ]Cat[ /b ]
[ /u ]Hat[ /u ]
[ b ]Boat[ /b ]
// insert form
function insertForm($content, $linkSet, $editPage) {
?>
 <script language="JavaScript"> 
 var choix_balise = new Array(3); 
 for(i=0;i<3;i++) { choix_balise[i] = false;} 
 function mk_ajouter(textarea, ms1, ms2,x) { 
 var tmpstr=''; 
 choix_balise[x]=!choix_balise[x]; 
 tmpstr=(choix_balise[x])?ms1:ms2; 
 if (document.selection) { 
 textarea.focus(); 
 sel = document.selection.createRange(); 
 if (sel.text.length == 0) { 
  sel.text = tmpstr; 
 } 
 else { 
  sel.text= tmpstr += sel.text + ms2; 
 } 
 } 
 } 
 </script>
 <form name="Content_Edit" method="post" action="<? echo $_SERVER['PHP_SELF'] . '?pageID=1&linkSet=' . $linkSet . '&editPage=' . $editPage; ?>">
 <p>
 <input name="b" type="button" Value="[b]" onClick="mk_ajouter(document.Content_Edit.textarea,'[b]','[/b]',1)">
 <input name="u" type="button" Value="[u]" onClick="mk_ajouter(document.Content_Edit.textarea,'[u]','[/u]',2)">
 <input name="i" type="button" Value="[i]" onClick="mk_ajouter(document.Content_Edit.textarea,'[i]','[/i]',3)">
 <input name="color" type="button" Value="[color=]" onClick="mk_ajouter(document.Content_Edit.textarea,'[color=]','[/color]',4)">
 <input name="size" type="button" Value="[size=]" onClick="mk_ajouter(document.Content_Edit.textarea,'[size=]','[/size]',5)">
 <input name="url" type="button" Value="[url=]" onClick="mk_ajouter(document.Content_Edit.textarea,'[url=','][/url]',6)">
 </p>
 <p> 
 <textarea name="textarea" cols="90" rows="50"><?php echo $content; ?></textarea>
 </p>
 <p> 
 <input type="submit" name="Submit" value="Submit">
 <input name="Reset" type="reset" id="Reset" value="Reset">
 </p>
 </form>

[Stuperfied]

Sorry, fixed.

sel.text= ms1 + sel.text + ms2;