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So color colon blue, for example, followed by a semicolon
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will change the color of this h1 element to blue.
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And my text editor is automatically showing me
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a little square that shows me what this color blue is actually
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going to look like.
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This isn't part of the text.
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It's just my text editor being helpful so
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that I can see in advance as I'm writing this code what the color is actually
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going to look like.
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So now if I open up style.html, here's what I see.
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Instead of a black heading at the top, we've changed the color to blue.
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And there are many other built-in colors that
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exist within HTML that we can use in order to change
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the color to whatever we want.
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If instead of blue, I said I want the color to be red,
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for instance, I can refresh the page.
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And now, the heading is red.
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And there are many other colors.
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I can change the color to like spring green, for instance.
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And that's going to be a particular shade
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of green that displays just like this.
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And so now, we have the ability to add various different style
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properties to individual elements.
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I can say take this heading and change its style
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so that the color instead of being black is going to show up as blue instead.
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And if I want to add multiple CSS properties to the same HTML element,
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I can do that as well.
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Here in the style attribute, I can say that in addition
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to saying that the color is blue, I'd like to give a second CSS
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property to this element.
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I'd like to say that the text align property should be center, for example.
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The text align property controls, as you might imagine,
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how a particular HTML element has its text aligned.
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Is it all the way on the left, all the way on the right, or centered?
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And if I change the text align property to have a value of center,
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well, then now, when I refresh this page, I see that Welcome to my web page
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is now both blue, and it's centered.
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I've changed the color, and I've changed the alignment
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of this particular element.
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And HTML elements don't need to just be styled directly.
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They can also get their style information from parent elements.
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So if you recall again that DOM structure, where
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we have an HTML element inside of which is this body element
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and inside of the body element is this h1 element and this text,
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you can imagine if we wanted this styling
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to apply not just to this heading, but also to the Hello World text,
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I could move the styling information, move this style attribute,
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change it from the h1 and escalating it to this body.
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And if I move the style to the body, then everything inside of the body
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is going to be styled in that way.
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So let's now take a look at an example of that to see how that works.
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If I take this style information, and I move
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it so that instead of associating it with the h1,
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I instead associate it with the body, then now, when I refresh the page,
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I see that both parts of the body, both the big heading
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at the top that says, Welcome to my web page,
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as well as the text, Hello World, both have those CSS properties applied.
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I've changed their color to blue.
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And I've also changed their text alignment
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to be centered instead of just left aligned.
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But if I do want it to just be that heading,
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then I can move it out and say that I just
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want to apply the style to that one individual heading.
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Now, one thing that we might imagine might become a problem over time
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is that imagine if I had multiple headings that I wanted
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to style in the same way, for example.
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Let's say I have a second heading that--
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this is a second heading--
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that I also want to be styled as blue and centered as well,
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I can refresh this page and see that right now that is not the case.
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And I don't want to make the entire page blue and centered.
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I only want these two headings to be blue and centered.
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So what I could do is I could just take this style code from the h1
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and apply it to this h1 as well, so that both of my h1 elements
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now have the exact same style code.
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And I'll go ahead and refresh this.
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And now, we see this is the intended behavior.
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I have two headings, both of which are centered and both of which are blue.
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But what we want to start to think about as we start to build web applications,
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and especially as our web applications start to get a little bit more
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sophisticated, is to think about the design
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of how we're building our web pages and how
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we're building our web applications.
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And in particular, anytime we find ourselves
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copying a lot of the same information from one place
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to another, that's probably not the best design.
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And you should start to think about how might you
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design this a little bit better.
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It's not great design, one, just because there's
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some redundancy that probably doesn't need to be there,
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but also because it makes the page a little bit more
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difficult to change and add a little more difficult to update.
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If I instead want to change both of these headings
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to be red instead of blue, then all of a sudden,
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I need to change my code in two places.
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I need to change the style attribute on this first heading up here.
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And I also need to change the style attribute
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on the second heading down there.
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What I'd like to do is to somehow just be
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able to write the style code once and then have
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