The HTML structure of webmail interfaces: Gmail, Hotmail, and Yahoo Mail

As part of the Zentact project I’ve been working on, we were asked to integrate with various webmail clients. This makes it easy to manage your contacts while sending email.

Doing this was a bit of a pain. Since all code is minified, and they all use Javascript events differently, there was a good bit of working to figure out the details. I wanted to share this info in a blog post for programmers who come along in the future. If you don’t know/care about HTML, Javascript events, the DOM, YUI, or AJAX, this post is not for you. Please enjoy one of my other fine posts, perhaps this post on military code names.

Before I begin: there was a ton of info learned (and already forgotten) about this process. This is not a complete guide, but is mostly a brain dump from implementing UI integration on three different webmail interfaces.

  • Gmail uses 6-character strings, [A-Za-z0-9] for all its classes. These classes remain the same from load-to-load, but I believe that they may change over time with minification. IDs are not as constant, and many are dynamically assigned. These start with a colon.
  • When you’re working with events, you may get inconsistent results. Some events are not fully propagated, they get captured and you can’t find out about them. If onclick doesn’t work, try listening for onmousedown or onmouseup. One of them may get you notified of the event you want. Same advice goes for onkeydown, onkeyup, and onkeypress. That being said, once you get into these, be sure to realize that these three events will occur in particular orders. Make sure you’ll be getting notified at the right time.
  • All of the webmail UIs use iframes. This lets them keep their code for loading the UI separate from the code to display the UI. I know there’s some cross-site scripting implications in this, but I’m not sure of all the details. Gmail’s loading screen (the loading bar they show you) is a different iframe than the one that shows you the inbox. All of these iframes are at the root of the document, and there’s nothing else in there.
  • You could use Firebug break points to pause the code and examine what’s going on, but nearly all JS is minified. Since breakpoints can only be set by line, and there’s multiple functions defined per line, it ends up not being helpful.
  • For its UI, Yahoo seems to use YUI, plus some other stuff on top of that. There’s some weird results because of this. The body of the email editor is a group of DIVs, some are invisible, some are for border decoration, and others are for the background of the editor.
  • When we inserted elements into Yahoo Mail using regular DOM operations, they would appear behind other page elements, until another part of the UI was interacted with, when the screen would redraw and then they would bump into place. YUI seems to have its own redraw/repaint functionality, and it won’t play nice with DOM manipulations.
  • Hotmail is strangely one of the less-exotic interfaces. They use consistent IDs. I don’t think they’re hand-coded, however, because they submit to a naming scheme that seems too machine-generated. But still, they are there, and you should take advantage of them.
  • When you’re using events, and you get notified of an event, use the event.originalTarget property to find out where in the DOM you are. That’s useful information when you’re dealing with a DOM tree of nonsense class names and IDs.
  • When you’re trying to figure out where in a DOM tree you are, don’t hesitate to go up several levels and check a great grandparent node, or a “cousin” node. Once you get a single point of reference, you can generally work out where everything else is, relative to it.
  • Some UIs open each message in its own iframe, which means that IDs are consistent since they’re in their own namespace.

Also, thanks to Nate Koechley for helping me get through some of the Yahoo details.

If you’ve got other questions, shoot me an email. I remember more stuff, but might need a good question to shake it loose.


Hey kids! Guess who’s presenting at Acts as Conference, 2009! These guys! Also, some guy with a big nose.

I’m giving a talk on OAuth, the greatest way to protect your APIs while keeping your users secure. Simple, easy, fun, and it might even get you laid. The amazing, spectacular, splendiforous OAuth! Yea. It’s gonna be that good.

And now, for the official marketing:

Acts as Conference 2009 is a two-day Rails conference that will make you a more competitive Rails developer by learning from those driving the innovation that is fueling the Rails community. Held February 6th and 7th in Orlando, Florida, Acts as Conference features a great speaker lineup, free food, a chance to meet with Rails innovators, and a live via video Q&A session with David Heinemeier Hansson. At $125 dollars and limited to 175 attendees, the conference will sell out fast, perhaps faster than last year. Register today at See you there!

Zentact reaches out to web and says hi. Web waves back.

It’s official, Zentact is live. This is the product that Cloudspace has been building for the past several months for John Sampson, Eric Marcoullier, and Jared Brandt (who also makes some damn fine wine).

The skinny of Zentact is that it’s an address book with a Firefox extension that lets you know when someone in your address book might be interested in the page you’re viewing. Go to the site and give it a whirl.

It has been an exciting day. Watching the comments roll in on Twitter is awesome, and so is watching the emails go out from Zentact.

Mashable loves us. So do the fine folks at ReadWriteWeb and VentureBeat. And finally, an excellent review of Zentact from Mr Howard Lindzon. Also, coverage from some unbiased sources, like Cloudspace. 😀

You should check it out. You’ll need a invite code, and you can use TIMZEN. Or, just sign up with this link, which magically includes the Zentact invite code. Let me know what you think.

A Javascript debugging tip for Firebug (or “Stop using alert()!”)

Did you know that if you’ve got Firebug for Firefox installed, you can use it for debugging your own code? By calling

console.log("Here's a message!");

Firebug will print the message to it’s internal message log. Neat!

Firebug message console

Now, that’s all good. But let’s say you’re on a project that’s not using a Javascript preprocessor to minify and strip debugging code — which would be the best option. You want the benefits of debugging, but not having to constantly remove debugging code for deployment. If a user doesn’t have Firebug installed, they won’t have a console object. So obviously leaving your debug code in is going to cause an error.

Or will it?

Try adding this code before any of your other Javascript. It will set up a fake console so that if Firebug is not installed, there won’t be any errors.

if(!console || !console.log) {
var console = new Array();
console.log = function () {}

Bonus idea! If you combine the idea shown here, with my previous post about debugging Firefox extensions, you can see how to prevent extension debugging from getting in the way of your users.

if(!Firebug || !Firebug.Console || !Firebug.Console.log) {
var Firebug = new Array();
Firebug.Console = new Array();
Firebug.Console.log = function () {}

How to use Extension Developer’s Extension in Firefox 3

Here’s a tip for developing Firefox Extensions in FF3.

You might have heard of the Extension Developer’s Extension (EDE). EDE is an extension that provides useful settings and features for people who are writing their own extensions. For example, EDE makes it easy to activate Javascript debug settings, interactively debug Javascript, and a few other goodies.

My personal favorite feature is the “Extension Builder” — it that lets you install a development copy of the extension . That is, you can run an extension from your working copy/dev folder. Without EDE, you’d have to — uninstall an extension, restart Firefox, install, restart — every time you wanted to test a change. With it, you can just restart Firefox one time, and your dev extension is reloaded. When doing heavy development, I have personally saved over an hour per day from this one feature.

The sad part is that this feature does not work in FF3. The option is just grayed out. But, there’s a workaround. Load up FF2 with the same profile that you use for FF3. Use EDE to install the extension from disk like you normally would. Then, quit FF2, and launch FF3. Since the extension is tied to your profile, FF3 will load your extension from your dev folder, just like in FF2.


Twitter Autocomplete (Tw-autocomplete Firefox Extension)

After lots of code, tests, and fun, I’ve produced a Firefox extension to add a useful, new feature to Twitter, as opposed to writing Twitter extensions as a joke 😀

Simply put, the extension provides autocomplete for Twitter usernames from your own list of friends while you’re using the web interface at It’s totally secure — no separate login required. Just install it, and use Twitter naturally.

When you start typing messages to people — using “@user” or “d user” — a list of matching contacts (along with icons) will drop in. You can click the person’s name to fill their username into the text box, or use the arrow keys along with tab/enter to select. As an added bonus, if you can’t remember their username at all, just type their first name, and the extension will figure it out.

There is another autocomplete script for Twitter, but it requires installing extra libraries, and I think this is simpler. Clearly it’s a feature in-demand.

The extension is hosted at, a highly reputable site. They also provide lots of great management features that are handy to developers. I hope you enjoy using Tw-autocomplete.

Javascript Events, the DOM, and Firefox/Gecko

OK, here’s the deal, as quick as I can put it, but with enough words that Google will correctly index this post and make this information easier to find for the next person who needs it.

Let’s say you’re developing a Firefox extension, and you need to look at the HTML of the page. You know that Firefox is constantly throwing event notifications — there’s the MouseEvent “click” when something is clicked, the KeyboardEvent “keyup” when a key is release, and so on.

So, you figure “well, I need the HTML of the page, so I’ll wait until it loads, then grab the source/parse the DOM tree/unleash flying monkeys”. You know that the style of

window.onload = the_function_name;

is bad, because it only lets one function receive the load event. So, you write some code like

gBrowser.addEventListener(“load”, the_function_name, true);

because this is what you want. You wait for the “load” event to fire, and then run your function. Test this code out, and it will work well-enough, most of the time. Sometimes, it lags, sometimes it doesn’t even fire at all. WTF? Well, I’ve been there.

Here’s the thing: the “load” event fires when loading is done. If you’re looking at the whole window/document, it’s not done loading until the whole document is loaded, including bandwith-and-time-heavy images. And these things can be slow to load, or hang entirely. This can seriously mess with the concept of “loading”. You don’t care about any of these things, you just want the HTML.

Well, Firefox is a very deep project, and there’s a few secret events that aren’t widely used or documented. If you want to know when the HTML is loaded — or more accurately, when the DOM Tree’s content is loaded — there’s a special event you can monitor: “DOMContentLoaded”

gBrowser.addEventListener(“DOMContentLoaded”, the_function_name, true);

This is a very reliable way of knowing when the browser has loaded only the page. The catch is that it’s Firefox-internal only. Which means it only works from an extension — you can’t use this in a web page. There are techniques for duplicating this functionality in other browsers, but that’s getting beyond this post.

Detecting page loads in a Firefox Extension

Detecting page loads is a useful ability. It’s easy enough to throw in a

gBrowser.addEventListener(“load”, function_name, true);

But, it causes extra events to get generated. There’s load events occurring in the browser that aren’t page loads. The trick to detecting real page loads (but not Back/Forward navigation when the page is still in memory — only page loads that have a server hit) is to look at the event’s target. In this example, “event” has been passed into the function specified in the addEventListener call above.

if(event.originalTarget instanceof HTMLDocument) {

will make sure that the load event came from a web page being loaded. You can even go a step further and filter out different types of HTMLDocuments.

if(event.originalTarget.defaultView.frameElement) {

will catch events that were triggered as the result of a frame or iframe. It’s an important step, because lots of advertising networks embed their ads in iframes, and you probably are more interested in the actual web page than the ads on that page.