Give this code a try, it may need some improvements, but it does the job. Remember to minify it and ensure you add "javascript:" before pasting it into your browser's address bar.
javascript: (function (e, a, g, h, f, c, b, d) {
if (!(f = e.jQuery) || g > f.fn.jquery || h(f)) {
c = a.createElement("script");
c.type = "text/javascript";
c.src = "http://ajax.googleapis.com/ajax/libs/jquery/" + g + "/jquery.min.js";
c.onload = c.onreadystatechange = function () {
if (!b && (!(d = this.readyState) || d == "loaded" || d == "complete")) {
h((f = e.jQuery).noConflict(1), b = 1);
f(c).remove()
}
};
a.documentElement.childNodes[0].appendChild(c)
}
})(window, document, "1.3.2", function ($, L) {
//your code here (a div with some content)
$("<div style='width:500px;height:400px; border:5px solid black; background-color:white; box-shadow:10px 10px 10px black; position:fixed; top: 150px; left:150px; z-index:99999'><h1 style='margin:150px'>hello world</h1></div>").appendTo("body");
});
UPDATE:
Check out this modification that utilizes an external document embedded in an iframe:
javascript: (function (e, a, g, h, f, c, b, d) {
if (!(f = e.jQuery) || g > f.fn.jquery || h(f)) {
c = a.createElement("script");
c.type = "text/javascript";
c.src = "http://ajax.googleapis.com/ajax/libs/jquery/" + g + "/jquery.min.js";
c.onload = c.onreadystatechange = function () {
if (!b && (!(d = this.readyState) || d == "loaded" || d == "complete")) {
h((f = e.jQuery).noConflict(1), b = 1);
f(c).remove()
}
};
a.documentElement.childNodes[0].appendChild(c);
$("<div style='width:500px;height:400px; border:5px solid black; background-color:white; box-shadow:10px 10px 10px black; position:fixed; top: 150px; left:150px; z-index:99999'><iframe style='width:100%; height:100%;' src='http://www.htmlcodetutorial.com/frames/hello.html'></iframe></div>").appendTo("body");
}
})(window, document, "1.3.2", function ($, L) {});