OK, how many ways can you think of, in order to solve our problem? Let's go over several solutions, and analyze their quality.
Some bad solutions
Solution #1 - hope for the best!
How can we solve the problem? The first solution may seem like a joke: do nothing, tell the user not to click twice, and hope for the best! Your page might look as Figure 2.1.
Figure 2.1. An actual screenshot of a page, just warning you against clicking more than once
This is a weasel way of avoiding the problem, but I've seen several websites that just warn the user about the risks of clicking more than once (see Figure 2.1) and actually do nothing to prevent the situation... the user got billed twice? we warned them... it's their...
