function htmlreplace(a,b,element){

    var nodes = (!element) ? document.body.childNodes : element.childNodes;

    for(var n=0;n<nodes.length;++n){
        if(nodes[n].nodeType==Node.TEXT_NODE){
            nodes[n].textContent = nodes[n].textContent.replace(new RegExp(a,'gi'),b);
        } else {
            htmlreplace(a,b,nodes[n]);
        }
    }
}

htmlreplace('[^ ]','g');