I was just reminded of another means of obscuring an email address which I neglected to mention in my previous Maximizing Ham article: displaying an email address as an image. By using an image such as 
instead of in-line text, you fool harvesters who see nothing but code. This trick was pretty popular a few years ago but I’ve been seeing it less these days, and for good reason. Email image replacement carries many of the same accessibility problems as any other image-for-text replacement:
- Screen readers for the blind will pass right over it if you neglect to include alt-text. And of course if that alt-text is the email address, you defeat your purpose. Luckily writing out an email address in plain English (slakemoth at example dot com) solves that problem, but then why even use an image? Some smarter harvesting bots may still recognize that text string as an email address unless you munge it further.
- The text will not scale, since it’s not actually text, just a picture of text. If your user prefers to read at 150%, they’ll have to squint and strain to read your teeny address. On a dedicated contact page you can just have a much larger email image on its own, but that’s not practical inline with other copy.
- Non-graphical browsers and visitors with images disabled will not see it, and will see the alt-text instead, so we’re right back to the whole “why use an image” thing.
- It can’t be cut-and-pasted into a mail client, but neither can munged text for that matter. Either way still creates more work for the user and more chance for human error. You can wrap your image in a clickable mailto: link, but that still requires the address to appear in the source code, so it’s no protection against spambots.
There are also some design issues making this a less-than-optimal technique. It defies the “separation of content and presentation” principles that web standards are moving towards. If you want to change the font-size or font-family on your site, you’ll need to recreate your email images to suit the new design. Placing pictures of text inline with other text can also wreak havoc on paragraphs, especially in liquid-width layouts.
It’s also not neccessarily the most secure approach. There are programs that can analyze an image and recognize the text displayed, intended to circumvent image captchas on secure systems. I’m not sure if such hacker tools are popular among spammers, but I wouldn’t be too surprised. I know there have been cases where an email address appearing in an image still makes it onto spam lists, but whether it was entered by a spammy hand or harvested by automata is hard to tell.
So all things considered, I just can’t recommend this technique. A contact form combined with an encoded address (as a backup option) is still the way to go.