Bad escaping of EOL

I am trying to work with a simple WYSIWYG editor. JSLint is saying it has "Bad escaping of EOL". Since I am new to javascript I am having a hard time figuring out what it means, since I am working with code found online. Can anyone tell me please what I should be doing instead of ending the line with a slash?

Here is the code in question: http://jsfiddle.net/spadez/KSA5e/9/

/*
 * WYSIWYG EDITOR BASED ON JQUERY RTE
 */

// define the rte light plugin
(function ($) {

    if (typeof $.fn.rte === "undefined") {

        var defaults = {
            content_css_url: "rte.css",
            dot_net_button_class: null,
            max_height: 350
        };

        $.fn.rte = function (options) {

            $.fn.rte.html = function (iframe) {
                return iframe.contentWindow.document.getElementsByTagName("body")[0].innerHTML;
            };

            // build main options before element iteration
            var opts = $.extend(defaults, options);

            // iterate and construct the RTEs
            return this.each(function () {
                var textarea = $(this);
                var iframe;
                var element_id = textarea.attr("id");

                // enable design mode
                function enableDesignMode() {

                    var content = textarea.val();

                    // Mozilla needs this to display caret
                    if ($.trim(content) === '') {
                        content = '<br />';
                    }

                    // already created? show/hide
                    if (iframe) {
                        console.log("already created");
                        textarea.hide();
                        $(iframe).contents().find("body").html(content);
                        $(iframe).show();
                        $("#toolbar-" + element_id).remove();
                        textarea.before(toolbar());