Why is @ sometimes in webpages written as [at]? Does it have any specific reason ?
At first it was a way to hide the e-mail addres from "robots" that search for e-mail addresses in all possible websites. It was a way to keep the e-mail public (for humans) but hidden (from robots).
Quickly ill-intended programmers were able to come around this safety, but still a lot of spam was kept out.
The safest way though to make your e-mail public is to save it as an image, and place it on the webpage instead of text. Not 100% effective, sure, but pretty safe and easy to do.