HTML Emails that Work

Successfully branding a web app requires carefully designing every aspect of its interaction with users. If you’ll be sending any emails to your customers, you’ll probably want to send something a little more impressive than simple plain-text. To do this, you’ll have to code an HTML email. This is not an easy task — making a complicated layout look good in a variety of email clients is an order of magnitude more challenging than making a website cross-browser compatible.

The main rule: forget everything you learned about CSS3 best-practices, and go back to how you coded websites ten years ago. If you don’t want to read past this second paragraph, here are the rules of thumb that inspired all the rest of the tips in this post:

  • Keep the total width of the email less than or equal to 600px. You can ensure this by enclosing the whole email in a table with a width attribute of “600”Use HTML formatting tags instead of CSS whenever possible.
  • All CSS that you do use (and it’s totally legitimate to use CSS for most things, just avoid positioning) must be inline. You can code your email with CSS in <style> tags in the <head> and then run it through Mailchimp’s free automatic CSS inliner tool to make this process a lot easier.
  • All email content must be entirely static — you can’t use any Javascript to help with layout.

Layout Without the Box Model

You can still achieve pretty complicated layouts without using CSS positioning, it just takes a bit more work to get everything to look good in a variety of email clients. Some HTML emails get around this layout problem by simply sending an email with a large picture that has all of the email content on it. While these emails are easy to create, avoid this temptation. Having all text in your email as actual text will help please spam filters, is much more user friendly, and will help email clients give relevant text previews of your email.

You’ll have to use tables to achieve anything other than very basic layouts. Using cellpadding, align, and valign attributes on table tags, you should be all set. Properly aligning text and images can be difficult and may require image slicing. Make sure that all images have “display: block” CSS applied to them, or else images that are meant to be displayed flush with each other will have a small separation between them in Gmail and Hotmail (for mysterious reasons).

Adjusting space above and below elements should, in most cases, be done with br tags. You can also use the line-height CSS attribute on p tags, just be sure to test this in a variety of email clients because many handle this attribute differently.

Styling Links

People tend to respond to default blue text links in emails, so don’t stray from this styling unless you have a good reason. If you do want custom links, be sure to define any custom colors within a font tag that is within the a tag. This is necessary because some email clients (like Gmail) make all links target=”_blank”, and in the process, strip out any color CSS you’ve added to the link.

Sometimes email clients will link text that you don’t want to be linked, such as text that looks like a URL or email addresses. There are two ways to deal with this:

  • You can control the style of the link by explicitly defining the text as a link and styling it appropriately.
  • You can enclose the text in an anchor tag without a href= attribute to make it behave like normal text and prevent it from being automatically linked. This won’t work in all email clients, most notably the iPad/iPhone.


The best way to include images in HTML emails is to host the image somewhere with a publicly-accessible URL, and use that full URL to refer to the image in the src attribute of an img tag. As explained above, all images should have the display: block CSS attribute so that Gmail and Hotmail handle them correctly without adding on extra space between images.

Resizing images isn’t smart in some email clients, i.e. if you just specify a width or a height for the image, it won’t preserve the aspect ratio of the image. If you want to display an image not in its original size, you’ll have to calculate both the width and the height of the image and explicitly write them in HTML. It’s good practice to define the width and the height in both the style attribute and the width and height attributes, because some email clients won’t recognize the width and height CSS definitions. The easiest way I’ve found to determine both the height and the width for an image given only one is to define one and then inspect the element with Chrome to determine the other measurement.

Even if the image will be displayed in its original size, it’s good practice to define the width and height anyway. Many email clients don’t display images by default, and by defining a width and height for the images, the placeholder that the client uses will be the proper size and won’t break your layout. In most email clients, specifying a background-color CSS attribute and a bgcolor img attribute will display a colored block instead of the default image placeholder before the image loads, which can greatly improve the look of your email when images are turned off.

Other Tips

  • It’s not currently possible to use fonts that aren’t installed on a user’s computer, i.e. font embedding won’t work
  • Avoid custom characters for <li> elements; it’s not possible to define pseudo-classes inline, and Gmail strips out the text-indent property, making it impossible to space it manually.
  • Use Mailchimp’s inbox inspection tool (not free) to see how your email looks in multiple email clients and OSs

Hunting Bugs or: How I Learned to Stop Worrying and Love git bisect

Getting assignments to write new features on a web app is always way more exciting than looking at Pivotal Tracker and seeing a list of bugs to fix. But I have to admit that probably the most satisfying feeling as a programmer is the feeling you get when you’ve solved a complicated bug in a clean way. I’m not talking about bugs that are caused by syntax errors or accidentally using the wrong methods. I’m talking about the bugs that have seemingly innocuous symptoms, but end up taking you deep into the rabbit hole of your app.

The work here is the hunt — once you’ve actually tracked down what’s causing the problem, it’s generally very easy to fix the issue. When you’re working on a large codebase with multiple contributors for an asynchronous web 3.0 app, this can get really interesting (and frustrating). What do you do when the problem isn’t immediately apparent?

About 25% of the time, you get lucky and Google does all of the work for you — simply copy and paste the error message that the application is giving you or type in a short description of the issue and you’ll be surprised how many people have encountered the same problem and have solved it already. Stack Overflow is a goldmine of bug solutions, and so is the vast ecosystem of tech bloggers (like me) who give you step-by-step instructions on how to solve bugs.

70% of the time, it’s a bit more of a challenge. The bug is specific to the way your team has set up the application and no one has encountered a bug quite like the one you’re currently facing. Google doesn’t help at all. Here’s where bug-hunting becomes much more of an art than a science.

Typically the process is fairly quick if you’ve written the code that you’re debugging — you already know what assumptions you’ve made in developing the feature and what events are firing when, and so strange behavior can often be tracked down fairly quickly. Luckily, you’re using git (right?), so even if you didn’t write the code you’re working with, you can quickly track down who did. Simply run git blame path/to/file in your console and git will output a line-by-line summary of who wrote each line of code.

If that doesn’t get you closer to a solution, the next step is to console.log (or its equivalent) everything. I’ve had the opportunity to see expert programmers hunt down bugs at, and that’s exactly what they do. There’s generally no need to use fancy debugging software or set breakpoints or anything complicated like that — just output to the console when events are firing, when methods are being called, and what the value of variables are at specific points in time. Obviously, you need to make educated guesses as to what might be causing the problem, and then figure out whether you’re right by outputting values to the console.

What about the last 5%? It’s reserved for the worst kind of bug. The bug that is impossible to fix. You’ve searched all over the internet and no one seems to ever have had the same problem. The code you’ve written and poured over is perfect and definitely is not the cause of the problem. The project you’re working on has thousands of lines of asynchronous code — literally anything could be going wrong and you have no leads whatsoever. Don’t worry, there’s still hope. git bisect is still your friend.

git bisect works when you know that a feature worked at one point in your app’s history and no longer works in your most recent commit. Don’t know offhand when the feature actually worked? git blame can help here — find out when the feature that’s no longer working was merged into master, and you can hopefully safely assume that the feature was working at that point.

Once you’ve located a good point and a bad point in your code, run git bisect start in your current branch. Then, since a git repository is basically a sorted list of previous states of your app’s codebase, git can perform a step-by-step binary search to find the first point in your app’s history where the feature stopped working. At each step, you run either git bisect good or git bisect bad in your console depending on whether the feature works or doesn’t work in the commit that git bisect picks. Eventually, the program will output the commit id of the commit that broke the feature. It’s an amazing feeling when you’ve been struggling with a bug for a day or two.

git bisect isn’t always that simple when you’re running it on an app that has a bunch of dependencies. Here’s how to get around any snags if you’re running git bisect on a rails app:

  • Restart your rails server and run bundle install at each commit that git bisect chooses. You might also need to manually compile assets at each point if something isn’t doing that for you automatically.
  • Make sure your “good” starting commit is the commit that merged the feature you’re debugging into master. Programmers don’t always commit 100% working code, but when it comes time to actually merge a pull request, you can be sure that the app ran smoothly and specs were passing.
  • Sometimes the app won’t run on old commits because paths in old versions of your Gemfile aren’t valid anymore. For example, when I used git bisect on’s codebase, a co-worker’s change to his Github username caused multiple bundle install failures. You’ll have to address these issues manually. If you can’t figure out why a gem isn’t installing, just replace the line with the corresponding line in the app’s most recent Gemfile.

Aside from those potential issues, git bisect feels like magic for those epic bugs that refuse to be solved. Once you’ve found the commit that broke the feature, you’re almost certainly 99% of the way to solving the problem.