What is valid XHTML and CSS?

In a previous article I talked about what is a website. In that article I mentioned that websites are made by HTML, XHTML and CSS.

Nowadays, a lot of websites are using the combination of XHTML and CSS.

But we can see a lot of websites that are using XHTML and CSS without following to the standard rules.

There is a way to check if that website follows to the standard rules of XHTML and CSS.

There is an organization that is providing us with the standard rules of XHTML and CSS. Just by typing the URL of the website you would like to check on their XHTML validator page or CSS validator page and click on the Check button, then you can see if that website is following to the standard rules or not.

You can see the following icons on the bottom of this website.

We could get these icons because we made this website by following to the standard rules of XHTML and CSS and passed the validation.

If you have a plan to make or renew your website, it must be difficult for you to find out which web design company is good. It may be a good way to judge that web design company if they are following to the standard rules of XHTML and CSS by using the XHTML or CSS validation service of the W3C.