What does the . mean in CSS?

I've read several tutorials on CSS, but none of the sites I've looked at 开发者_StackOverflowmentions or explains what a "." means in CSS.

What does the . mean?

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Nothing without context.

I'll hazard a guess that you are referring to a class selector.

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Well, in the following context:

.foo {
   //properties
}

it indicates that foo is a class. A # means it's an id and if it has nothing it means that it is for all tags of that type. So, in html, you would implement something with a "." like this:

<div class = "foo"></div>

For a "#" it would be

<div id = "foo"></div>

Use class/"." if you want to apply it to more than one thing. Use id/"#" if you want it to apply to one thing.

Ok, so if your wondering what a class is: A class is one of the three (I think it's 3) types of ways you select stuff in css. The id (which I explained) says that the following properties apply to anything (usually one thing) with 'id="foo"' in its tag. A class selector means that it applies to everything with a "class="foo"" in its tag. If it has none of these than it means that it applies to all things with that name.

.foo { //applies to all things with "class="foo"" in tag.
    border: black thin solid // applies a black border to them.
}
#foo { //applies to all things with "id="foo"" in tag.
    border: black thin solid // applies a black border to them.
}
div{ //applies to all div tags.
    border: black thin solid // applies a black border to them.
}
h1{ //applies to all h1 tags
    border: black thin solid // applies a black border to them.
}

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It is a class selector. Means the rule should be applied to all elements that have an attribute class with the value after the ..