<script type="text/javascript" src="../jscripts/tiny_mce/tiny_mce.js"></script>
<script type="text/javascript">        tinyMCE.init({
            //elements: "txtField1,txtField2",
            editor_deselector: "mceNoEditor",
            mode: "textareas",
            theme: "advanced",
            plugins: "safari,style,spellchecker,searchreplace,print,paste,directionality,fullscreen,noneditable,nonbreaking,xhtmlxtras,template",
            // Theme options   
            theme_advanced_buttons1: "bold,italic,underline,strikethrough,forecolor,|,justifyleft,justifycenter,justifyright,justifyfull,formatselect,fontselect,fontsizeselect",
            theme_advanced_buttons2: "cut,copy,paste,pastetext,pasteword,|,search,replace,|,bullist,numlist,|,outdent,indent,|,undo,redo,|,spellchecker,|,ltr,rtl,|,fullscreen",
            theme_advanced_buttons3: "",
            theme_advanced_toolbar_location: "external",
            theme_advanced_toolbar_align: "left",
            //theme_advanced_statusbar_location: "bottom",
            theme_advanced_resizing: false,
            //theme_advanced_disable: "sup,sub,removeformat,hr,|,charmap,image",
            // Example content CSS (should be your site CSS)
            content_css: "../Stylesheets/Style.css",
            editor_css: "../JScripts/tiny_mce/themes/advanced/skins/default/tinyMCEUi.css",
            width: "100%",
            //height: "200",
            spellchecker_rpc_url: "../TinyMCEHandler.aspx?module=SpellChecker",
            readonly: '<%=myReadonly %>',
            //onchange_callback: "tinyMceOnChange",//for counter
            //handle_event_callback: "tinyMceEventHandler"//for counter
            paste_retain_style_properties: "font-size,font-family,font-style,color"
        });
</script>

TinyMCE configuration for rich textbox

JavaScript