Be warned that bad people can easily avoid any javascript validaton.
Protect yourself by validating from the server-side first.
After the server-side validation works as expected, use javascript to improve the user experience and let them know about issues before they post the form.
Do you know of any tutorial that explains how to do that?(:
Here’s an example of using PHP to perform validation.
For javascript validation, it’s useful to use a ready-baked solution such as jQuery’s validate plugin, where people have already solved many of the issues that can occur.
Thank you. I’ll check them out when designing the registration page!
The reason for having an external style sheet (as opposed to placing the page styles in the head of the document) is that it can be used for all the pages on the website, so that you can change styles for every page in one location.
If your site were only one page, it would be just as good to have your styles in the head of the page itself. There’s nothing wrong with doing this; it’s just less efficient is you have multiple pages.
Pheeeeep!! Time out!
When the style is in the head then it is downloaded on every occasion with the page. Placing the styles in a separate file allow the stylesheet to be cached by the user’s browser, which lessens the amount they have to download and lessens the amount that your own server has to provide.
Place stylesheet declarations within their own separate file. No excuses 
Indeed. I wasn’t recommending it. I was mainly just noting that for a one-page site it wouldn’t make any difference—and that it’s not technically wrong, just inefficient for multi-page sites. But yes, for multiple pages, the extra downloads and lack of cashing is another reason not to have styles in the head.
But it does make a difference.
When a single page loads, and that single page contains a reference to an external stylesheet, the web browser checks to see if it already has the stylesheet in its local cache.
Multiple visits to that one page from same person will result in the cached stylesheet being used, instead of having to be re-downloaded over and over again with the main content of the page.
OK, you win!
Hurrah! :award:
We’ll ask Raena to put it above your avatar. 