fckconfig.js 

// ORIGINAL 
// FCKConfig.FontSizes		= '1/xx-small;2/x-small;3/small;4/medium;5/large;6/x-large;7/xx-large' ;
FCKConfig.FontSizes		= '1/5;2/6;3/7;4/8;5/9;6/10;7/11;8/12;9/14;10/16;11/18;12/20;13/24;14/28;15/30;16/60;17/90' ;




fck_othercommands.js 






FCKFontSizeCommand.prototype.Execute = function( fontSize )
{
//ORIGINAL 
//      if ( typeof( fontSize ) == 'string' ) fontSize = parseInt(fontSize, 10) ;
//
//	if ( fontSize == null || fontSize == '' )
//	{
//		// TODO: Remove font size attribute (Now it works with size 3. Will it work forever?)
//		FCK.ExecuteNamedCommand( 'FontSize', 3 ) ;
//	}
//	else {
//            FCK.ExecuteNamedCommand( 'FontSize', fontSize ) ;
//      }


// CHANGED CODE 
	var oSel = null;
	var bHasSelection = false;

        if ( typeof( fontSize ) == 'string' ) fontSize = parseInt(fontSize, 10) ;

	var e = FCK.EditorDocument.createElement( 'SPAN' ) ;

	if ( fontSize == null || fontSize == '' ) {
		e.style.fontSize = '3px';
	} else {
		e.style.fontSize = fontSize + 'px';
	}
	try{ 
		if(document.all) { 
			oSel = FCK.EditorDocument.selection ; // ie 
			bHasSelection = !(oSel.type == "None"); 
		} else { 				
			oSel = FCK.EditorWindow.getSelection() ; // gecko 
			bHasSelection = (oSel && oSel.rangeCount == 1 && oSel.getRangeAt(0).cloneContents().childNodes.length > 0); 
		} 
	} catch (e) {} 
	if( bHasSelection  )  {
		//if (FCK.EditorDocument.setSelectionRange) 
		if (document.selection && document.selection.createRange) { // IE code goes here
			var range = FCK.EditorDocument.selection.createRange();
			e.innerHTML  = FCK.EditorDocument.selection.createRange().text;					
		} else {
			FCK.EditorWindow.getSelection() ;
			e.innerHTML  = FCK.EditorWindow.getSelection();
		}
		FCK.InsertElement( e );				
	}


}