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In this video we're going to talk about sizing fonts and this is a subject that could rightfully occupy it's own book probably or an entire video title, just talking about fonts and font sizing and all of the ins and outs, but the basics are really very simple. You can make an element have a font size that's either a specific length, let's say 12 pixels or is related to its parent element. That's a good starting point. Let's take the h1 in the content area and the content, main content, of the document, give it a font let's say 200 pixels and what this means is the font size of this h1 should be 200% the font size of that h1's parent element.
If we scroll down a bit we see this h1 right here. Its parent element is actually the div with the id of content, so the font size of the h1 will be 200% the font size of the div with the id of content. And if we load, there you go, it's twice the size, 200% or twice the size. What I just didn't in CSS terms is exactly functionally equivalent to saying 2em, 2em, 200% either way it's twice the size of the parent element. So I could do content h2, font size 1.5em or 150%.
And then there we go that's the h2's parent element again is that div with the id of content. So the h2 will be half again as big or 1 1/2 times the font size for that div. Now, you are not constrained to ems and percentages, you could for example say I want font size of paragraphs to be smaller, and that would make them smaller. Again, this is related to the parent elements, so if these paragraphs whose parent is that content div the font size of the paragraphs is smaller than that of the content div, but how much smaller isn't explicitly defined by the CSS specification is simply has to be smaller, it could be just a little tiny bit smaller, it could be a whole lot smaller. In practice, smaller usually comes out to be around 0.85em but it's not always precisely equivalent and I would be nice if at this point I could say and here are the situations in which there are differences, but it's not quite that simple.
The algorithms don't seem to be that easily analyzable. So, you just sort of taken off if the font size is around 0.85em in terms of its effects and you say things like smaller because you don't really care exactly how much smaller the paragraph's font size is going to be or whatever element, you don't care how much smaller is going to be, it just needs to be smaller. There's also larger, not bigger, but larger which is the opposite effect, it's larger than it's parent element's font size. How much larger? Not really specified.
usually in the vicinity of around 1 1/4 to 1.2em 120% to 125%, but that's not guaranteed, it could be 133% in some obscure browser you never heard of. So, using things like smaller and larger again only if you don't care to be very precise about how much smaller or larger a font size should be because we can see here, let's say font size 85%. That's very similar to smaller, but did you notice there was a slight difference there, very slight.
If we go from smaller back to 85% I'm going to hit Reload and watch right in the first paragraph right sort of near the fourth line or so. See that, is this tiny little change. That's what I mean, it's very difficult to analyze exactly what's going on there. There are other keywords besides larger and smaller. There's also just plain old small font size small, which you might say okay, that's exactly the same as smaller but not really because suppose instead of making the paragraph font size small I just make the body font size small and you'll notice everything sort of skills in relation to that.
Basically there are seven keywords they go X.X.small for extra extra small, x.small, small, medium, large, x.large and x.x.large, and exactly what those correspond to is left up to each individual browser. Every browser could do x.x.large as a completely different size, as long as x.x.large was larger than x.large which was in turn larger than large, which was larger than medium and so on. The default, according to CSS for font size, is medium that should give you whatever the default is for your browser and small should be smaller than that.
You can use keywords, you can use percentages, you can use ems if you like. There's one thing to watch out for though. I'm going to back to same body font size small and I'm going to say paragraph font size 85%. Notice that the paragraphs have gotten tinier. Here is the reason, because the body has been set to a font size off small. Alright, and so that gets inherited by it's descended elements, so the content div inherits the font size of small and then the h1 sets itself to be twice whatever small means and the h2 sets itself to be 150% whatever small means. The paragraphs sets itself to be 85% of small so what I've really done I've said ok, make the body small but then make the paragraph smaller than that.
Alright, if I were to take this even further and do something you know, potentially disastrous like content font-size smaller the paragraphs get teeny teeny tiny and nobody can read them. This is entirely possible, so one of the things you want to watch out for with font sizes is it if you have situations where you're accidentally nesting changes in font size you can get these sort of runaway effects. Now there are some web browsers that will enforce minimum font sizes. Safari, for example, on the Macintosh has a- will let you stop smallest of text, basically you can say it 9 pixels or 8 pixels or whatever size. Don't make text any smaller. I don't care what the CSS says, but other browsers for example Firefox here don't have those kinds of limits so, if we squint really hard and we pretend that that this was all written by houseflies, we can sort of make out that it says the history of tea extends so far into the past that it's very origins are shrouded by legend, but of course part of that is the fact that I'm very familiar with this text and so I can't make out what it says, you would never ever want to present this to a user.
So, there's no particular fix for this, necessarily, except being careful and not nesting relative changes in font size. You might think to yourself, well geez, why would I ever do that? Who would ever get caught by that? That's actually easier than you think because suppose you had a series of nested lists, lists inside of lists inside of lists and an outline of something like a core syllabus and you said all unordered lists should be a font size of smaller or an unordered list should have a font size of 85%. Well, a third level nested list would be 85% of 85% of 85%, which is teeny tiny and basically unreadable.
So that's something you want to watch out for font sizing. So, like I say, I mean the basic of font sizing are very simple. But sort of these combinations of being careful about nesting and the fact that if you have things get smaller and smaller and smaller things can become unreadable. That's where there's really no substitute except a lot of experience at doing this sort of things and there can be an entire training course and book just about fonts and font sizing and so, absent that, making mistakes is actually the best way to learn and believe me I have made many many font sizing mistakes in my career and still do on occasion, it can be easy, even if you're someone who's done it for very long time to forget that Oh that's right, I do have three levels of nested lists and so when I made this font size change I didn't really think about what the effect would be.
There is a, I'll just give you a quick tip. Suppose you want your list to be smaller for some reason. But you want all your lists to be the same size, right now they're just getting smaller and smaller and smaller the further you nest them, but with the descendent selector you can do this. So, any unordered list should have a font-size as smaller, but any unordered list that's inside an unordered list should have a font size of 1em, which basically stops that whole smaller thing so the top-level unordered list becomes smaller within any nested lists inside of it with the font size 1em, basically pick-up what smaller meant and they all stay the same size consistently.
So just a little tip there, something that I picked up through years and years of font sizing mistakes and hopefully will allow you to avoid making many of the same mistakes.
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