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The "HTML Validator" Lesson is part of the full, Introduction to HTML course featured in this preview video. Here's what you'd learn in this lesson's course:

Jen introduces HTML validators that check for coding mistakes within a web page.

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Transcript from the "HTML Validator" Lesson

>> Jen Kramer: So the validator is something that I should tell you about right now. The validator is a really important thing that will check your HTML and make sure that you didn't make any mistakes. [NOISE] How cool is that? A mistake checker, okay? So let's look at how this works.

>> Jen Kramer: So this is the link right from our lecture notes, just before exercises, this is, and if you hop on into here, this is the W3C. These are the people who write all the specifications for the web. These are the ones who create all the standards, such that web browsers work, that we write code that is understandable, these are the guys that establish it.

And they are going to, probably the best way for you to do this today is just validate by direct input. So here on this webpage, come to Validate by Direct Input, and then you can go to your code, highlight it all, copy it.
>> Jen Kramer: Paste it into your box.

>> Jen Kramer: And say Check, and it's gonna check your HTML, and see if you made any mistakes. Now this is gonna tell me that I didn't make any mistakes. So, yay. All right? But the validator has limitations. What are its limitations? Can anyone think of limitations that a robot might have in looking at code?

>> Speaker 2: Misspelling.
>> Jen Kramer: It's not gonna catch your misspellings. It is not a spell checker. What else? Is it gonna catch bad file paths?
>> Speaker 3: Probably not.
>> Jen Kramer: Nope. It could care less what your file paths are. It's not gonna check those. Is it gonna check that you used the right tag, that you used an ordered list where you should, or un ordered list where you should?

Is it gonna catch that? Nope. It's just gonna say yep, it looks like a list. You wrote it correctly. Good job. So there are some limitations here, but if you get stuck writing your HTML, the very first thing I tell you to do is to check and make sure you haven't made any mistakes, and this is a very quick and easy way of doing it.

Sometimes it'll find that tag you didn't close, or the misspelling that you have in your tag, a misspelled attributes, that'll find an answer for you. Makes sense?