Run this in the devtools console on a SharePoint 2010 page when in edit mode, to strip out quite a lot of spurious crap from the HTML.

Strip out spurious HTML.js

/*
    Run this in the devtools console on a SharePoint 2010 page when in edit mode, to strip out quite a lot of spurious crap from the HTML.
*/
(function($, window, document) {

    var $editables = $("[contenteditable], input[type='hidden'][id*='hiddenStorage'], input[type='hidden'][id*='hiddenDisplay'], input[type='hidden'][id^='ctl00'][id$='content']"),
        originalHTML,
        filterHTML,
        $el,
        $filterHTML,
        $removeElements,
        elType;

    $editables.each(function (i, el) {

        $el = $(el);
        elType = $el[0].tagName.toLowerCase();

        originalHTML = '';

        // It'll be an input or a div...
        if (elType === 'div') {
            originalHTML = $el.prop('outerHTML');
        } else {
            originalHTML = "<div>" + $el.val() + "</div>";
        }

        filterHTML = originalHTML;

        // Strip out zero width spaces - see http://stackoverflow.com/a/11305926/13019
        filterHTML = filterHTML.replace(/[\u200B-\u200D\uFEFF]/g, '');

        // Strip out bad HTML classes
        $filterHTML = $(filterHTML);

        // Work around side effect - SharePoint WYSIWYG can break with empty <td> elements
        $filterHTML.find("td:empty").each(function() {
            $(this).text("\u200B");
        });

        // Filter out legacy table styles
        $filterHTML.find("[class*='ms-rteTable']").removeAttr("class");
        $filterHTML.find("[class*='sbgTable']").removeAttr("class");
        
        // Remove crappy style attributes
        $filterHTML.find("[style]").removeAttr("style");
        
        // Remove spurious rubbish
        $filterHTML.find("[rowspan='1']").removeAttr("rowspan");
        $filterHTML.find("[colspan='1']").removeAttr("colspan");
        $filterHTML.find("[_moz_resizing]").removeAttr("_moz_resizing");
        $filterHTML.find("[_moz_abspos]").removeAttr("_moz_abspos");

        // Remove empty elements
        $filterHTML
            .find("div, p, br")
            .not("[fragmentid] *, [fragmentid]")
            .filter(":empty, br:last-child")
            .remove();
        
        // Remove whitespace-only elements
        $filterHTML
            .find("div, p, br")
            .not("[fragmentid] *, [fragmentid]")
            .filter(function() {
                return ! $.trim($(this).text());
            })
            .remove();

        // Remove useless span elements added by the RTE and not cleaned up
        $filterHTML
            .find("span")
            .filter(function() {
                return $(this)[0].attributes.length === 0;
            })
            .each(function(i, el) {
                $(el).replaceWith($(el).html());
            });

        filterHTML = $filterHTML.html();

        if (originalHTML === filterHTML) {
            console.info("No changes made.");
        } else {
            console.warn("Made changes!");
            console.log("B: " + originalHTML);
            console.log("A: " + filterHTML);
        }

        // It'll be an input or a div...
        if (elType === 'div') {
            $el.html(filterHTML)
        } else {
            $el.val(filterHTML);
        }

    });

} (window.jQuery, window, document));