In CSS selectors: the difference between class and ID selectors_html/css_WEB-ITnose

Same points: can be applied to any element

Differences:

1, ID selector only Can be used once in a document . Unlike class selectors, ID selectors can only be used once, and only once, in an HTML document. Class selectors can be used multiple times.

The following code is correct:

China is a great country. . . . . Xi Jinping is the current president of the country

And the following code is wrong:

China is a great country. . . . . Xi Jinping is the current President of the country

2, You can use the class selector word list method to set multiple styles for an element at the same time. We can set multiple styles for one element at the same time, but this can only be achieved using class selectors, not ID selectors (ID word lists cannot be used).

The following code is correct (see the code editor on the right for the complete code)

.stress{    color:red;}.bigsize{    font-size:25px;}<p>到了<span <strong>class="stress bigsize"</strong>>三年级</span>下学期时，我们班上了一节公开课...</p>

The following code is incorrect (See the code editor on the right for the complete code)

#stressid{    color:red;}#bigsizeid{    font-size:25px;}<p>到了<span <strong>id="stressid bigsizeid"</strong>>三年级</span>下学期时，我们班上了一节公开课...</p>

ArrivedThird gradeNext semester. (This is feasible)

Note: The above code can put color:red and font-size:25px; in a class selector. If you want to set a word It is much more convenient to set the color to red and set its font to 25px; but if a place only needs to set its color to red, then it is better to use a class selector, so the more detailed it is when writing a class selector. The better (I think)! ! !