Why write 'at' and 'dot' in email rather than '@' and '.'?

This is one of the many anti-harvesting techniques used against automated spambots. This one is used massively, so there are lot of spambots used to it and it does not work 100%. You can see some statistics and comparison of various anti-harvesting techniques in this great article

https://web.archive.org/web/20180811103545/http://techblog.tilllate.com/2008/07/20/ten-methods-to-obfuscate-e-mail-addresses-compared/

I personally prefer the css display:none technique combined with javascript. See the example:

<a href="mailto:[email protected]">myemail@<span style="display:none;">ignoreme-</span>example.com

And use javascript to remove it from href element. This way it works for users with javascript enabled, and users with disabled javascript at least see address correctly, but of course, clicking does not work correctly.

Typically people do this to avoid having their email addresses found by spambots that search for a regex that matches email address formatting. By using _AT_ and _DOT_, the symbols that the spambot is looking for will not show up on the page, and therefore your email address will not be found.

It's generally good practice if you want to avoid an inbox full of spam. and you give out your email address on public pages. However, you can avoid the issue altogether by not posting your email address on a public forum. If you want to give it to someone, send it by a private message or email or something.

This is to obfuscate the Mailadresses from Mail-harvesters.