Enable tabbing inside textarea

<textarea name="content" class="textarea" id="content" rows="20" cols="65"  wrap="on" onKeyDown="return catchTab(this,event)"></textarea>

function setSelectionRange(input, selectionStart, selectionEnd) {
	      if (input.setSelectionRange) {
		input.focus();
		input.setSelectionRange(selectionStart, selectionEnd);
	      }
	      else if (input.createTextRange) {
		var range = input.createTextRange();
		range.collapse(true);
		range.moveEnd('character', selectionEnd);
		range.moveStart('character', selectionStart);
		range.select();
	      }
	    }

	    function replaceSelection (input, replaceString) {
		    if (input.setSelectionRange) {
			    var selectionStart = input.selectionStart;
			    var selectionEnd = input.selectionEnd;
			    input.value = input.value.substring(0, selectionStart)+ replaceString + input.value.substring(selectionEnd);

			    if (selectionStart != selectionEnd){
				    setSelectionRange(input, selectionStart, selectionStart + 	replaceString.length);
			    }else{
				    setSelectionRange(input, selectionStart + replaceString.length, selectionStart + replaceString.length);
			    }

		    }else if (document.selection) {
			    var range = document.selection.createRange();

			    if (range.parentElement() == input) {
				    var isCollapsed = range.text == '';
				    range.text = replaceString;

				     if (!isCollapsed)  {
					    range.moveStart('character', -replaceString.length);
					    range.select();
				    }
			    }
		    }
	    }


	    // We are going to catch the TAB key so that we can use it, Hooray!
	    function catchTab(item,e){
		    if(navigator.userAgent.match("Gecko")){
			    c=e.which;
		    }else{
			    c=e.keyCode;
		    }
		    if(c==9){
			    replaceSelection(item,String.fromCharCode(9));
			    setTimeout("document.getElementById('"+item.id+"').focus();",0);
			    return false;
		    }

	    }