Html5 css selector well number, difference between periods, html5 Selector

Html5 css selector well number, difference between periods, html5 Selector

I. Understand the style composition of CSS
Style sheets in CSS are composed of rules. Each rule consists of three parts:
1. selector (for example, "body" in the following example) to tell the browser which part of the document is affected by the rule;
2. attributes (such as font-family and color in the instance) specify what aspects of the layout are set;
3. The value (for example, Arial, sans-serif, #333333, etc. in the instance) gives the value of the style attribute.
 
Ii. Differences between different symbols in CSS styles

# Is the ID selector. Is the class selector * is the wildcard number
For example, * {margin: 0; padding: 0; all elements will follow this attribute style} (another case is IE hack. B {margin: 0; * margin: 10px;} Here, IE sees margin: 10px. other browsers will see the previous margin: 0;
 

Let's take a look at the code ~

body{font-family: Arial,sans-serif;color: #333333;line-height: 1.166; margin: 0px; padding: 0px;}#masthead{margin: 0;padding: 10px 0px;border-bottom: 1px solid #cccccc;width: 100%;}.feature img{float: left;padding: 0px 10px 0px 0px; margin: 0 5px 5px 0;}

# Id
Point number corresponds to class
Without adding html tags
In one sentence, the Class can be used repeatedly, and the ID can only be used once on a page. It is possible that the same ID will not be used repeatedly in many browsers, but it is definitely incorrect in terms of standards, and it may lead to practical problems in some browsers.
In practical application, the Class may be useful for text layout, and the ID is useful for macro layout and design of various elements.

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