Validation Programs on the Web

There is a really handy tool for HTML and CSS validation that I was reminded about very recently in a comment on one of my other posts. I personally learned about this tool in the fall of 2011 when I was first starting out in web design.(admittedly, before I realized how much I enjoy it.) I felt, after being reminded of this tool and its usefulness, that I should share it with others who may have not seen the comment that it was posted on. There are actually 2 different tools here, but they are both found on the same page. This is the page of the World Wide Web Consortium(W3C for short), which typically sets the standards used in web coding. The URL for their home page is www.w3c.org. The page can be a bit overwhelming to handle though, so I am going to provide direct links to the validation pages.

HTML: http://validator.w3.org/

CSS: http://jigsaw.w3.org/css-validator/

What these pages do, is that they allow you to enter your code in a couple of different ways, and then they verify the coding and ensure that you have no errors. You can enter your code in 3 ways.
You can enter the URL of the site itself, if it is currently on the web.
You can upload the file directly from your computer.
Or you can enter the code manually into a text box on the site.