What does tag mean in css

In CSS, tag represents a selector, such as "#tag{style code;}" and ".tag{style code}". TAG tags are self-defined keywords that are more accurate and specific than classification and can summarize the main content of the article.

The operating environment of this tutorial: Windows 7 system, CSS3&&HTML5 version, Dell G3 computer.

In css tag represents a selector, for example

#tag{样式代码;}
.tag{样式代码}

Each css style definition consists of two parts, the form is as follows: [code] selector {style} [/code] in { The part before } is the "selector". The "selector" specifies the object of the "style" in {}, that is, which elements in the web page the "style" acts on.

Category selector

The class selector selects based on the class name

It is marked with "." in front, such as:

.demoDiv{
color:#FF0000;
}

In HTML, elements can define a class attribute.

For example:

<div class="demoDiv">
这个区域字体颜色为红色
</div>

At the same time, we can define another element:

<p class="demoDiv">
这个段落字体颜色为红色
</p>

Finally, browsing with a browser, we can find that all elements with class demoDiv are applied this style. Including div elements and p elements in the page.

In the above example, we defined classes for both elements, but if there are many elements that will apply this element, then we have to define the elements one by one, which will cause too much repeated code on the page. This phenomenon It's called "multiple syndromes."

We can change it to define it like this.

<div class="demoDiv">
<div>
这个区域字体颜色为红色
</div>
同时，我们可以再定义一个元素：
<p>
这个段落字体颜色为红色
</p>
</div>

In this way, we just define a class and apply the style to all elements.

ID Selector

The ID selector can specify a specific style for HTML elements marked with a specific ID. Selecting elements based on their ID is unique, which means that the same ID can only appear once in the same document page. For example, if you set the ID value of an element to "navi", then you cannot change it again on the same page. The other element IDs are named "navi". Although you will find that even if you name several elements with the same id name, the css selector will still select these elements to apply styles (such as the class selector). For css selectors, the uniqueness of the id attribute does not seem to be the same. exist. However, for js, it will only select the first element with the same id name. As a good programming practice, the same ID should not appear twice on the page.

is marked with a "#" sign in front, which can be defined in the style as follows:

#demoDiv{
color:#FF0000;
}

This represents the font color of the element with the id of demoDiv set to red.

We define an element on the page and define its ID as demoDiv, such as:

<div id="demoDiv">
这个区域字体颜色为红色
</div>

Browse with a browser, we can see that the color in the area turns red

Define another area

<div>
这个区域没有定义颜色
</div>

Browse with a browser. As expected, no style is applied to the area, so the font color in the area is still the default color black.

Recommended learning: css video tutorial

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