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This article will take you through HTML comments and colors, and share some commonly used color names and hexadecimal values. I hope it will be helpful to everyone!
1. HTML comments (with examples)
HTML comments are mainly used to comment on the text in the document. The code is explained, and the comments are also part of the code, but the browser automatically ignores the content of the comments, so users cannot see the comments on the web page.
We should make good use of comments when writing code, because a complete HTML document often consists of hundreds or thousands of lines of code, and it may take a long time when we want to modify a certain part of it. Only then can you find the place you want to modify. With comments, it's different. We can divide the program into several parts according to functions or other conditions and mark them with comments. This can help you and others read your code and improve the readability of the code.
Single-line comments
In HTML you can use <!-- --> to add comments in the code, <!-- and --> Everything between ; is treated as a comment. The sample code is as follows:
<!DOCTYPE html>
<html>
<!-- head 开始 -->
<head>
<meta charset="UTF-8"> <!-- 当前文档采用UTF-8编码 -->
<title>HTML注释的写法</title>
</head>
<!-- head 结束 -->
<!-- body 开始 -->
<body>
<!-- 一段文本 -->
<p>欢迎来到PHP中文网</p>
</body>
<!-- body 结束 -->
</html>Comments can appear anywhere in the HTML document, including at the beginning of the document, at the end of the document, in the middle of the document, outside the tag, within the tag content, etc.
Multi-line comments
We mainly demonstrated single-line comments before, but multi-line comments are also supported in HTML. The difference between multi-line comments and single-line comments is not big. We only need to ensure that the content of the comment is between <!-- and -->, as shown below ：
<!--
多行注释
-->In addition to explaining the code, comments can also be used to annotate the code in the program. For example, when you don’t want a certain piece of code to be executed, you can comment it out first so that the browser can This code will not be executed.
IE Conditional Comments
Conditional comments are only valid in the Internet Explorer (IE) browser on Windows systems, other browsers will ignore them. Starting from IE5, conditional comments are supported. You can use conditional comments to provide some instructions to users using the IE browser. As shown below:
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>IE浏览器条件注释</title>
</head>
<body>
<h4>根据不同的 IE 版本显示不同的内容</h4>
<!-- 如果使用 IE，则显示 -->
<!--[if IE]>
<p>您正在使用IE浏览器</p>
<![endif]-->
<!-- 如果使用 IE8，则显示 -->
<!--[if IE 8]>
<p>您正在使用 IE8</p>
<![endif]-->
<!-- 如果不是使用 IE7，则显示 -->
<!--[if !IE 7]>
<p>您使用的不是 IE7</p>
<![endif]-->
<!-- 如果版本小于 IE10，则显示 -->
<!--[if lt IE 10]>
<p>您正在使用 IE10 以下的版本</p>
<![endif]-->
<!-- 如果版本大于等于 IE6，则显示 -->
<!--[if gte IE 6]>
<p>您正在使用 IE6 及其以上的版本</p>
<![endif]-->
</body>
</html>Running effect under IE8:
Running effect under Chrome browser:
Conditional comments can detect whether the current browser is IE and the IE version. Developers can load different style sheets or JS scripts according to different IE browsers.
Comparing IE versions will use the following keywords:
lt: The abbreviation of less than, which means less than.
lte: Abbreviation for less than or equal to, which means less than or equal to.
gt: The abbreviation of greater than, which means greater than.
gte: Abbreviation for greater than or equal to, which means greater than or equal to.
!: Not equal to
IE browser is not very friendly to HTML5 support, and the behavior of lower versions is even weirder. IE has gradually withdrawn In the market, major Internet giants are no longer compatible with IE, and everyone does not need to focus on IE during the development process.
2. Setting the HTML color value
HTML color is a mixture of red, green, and blue.
1. Browsers all support color name sets. The color value is a keyword or a number in RGB format, which is often used in the middle of web pages.
2. Use English words as color values:
red red | green | blue | pink | purple, etc.
3. Six-digit hexadecimal color value:
ff0000 Abbreviation: #f00
The first two digits represent red, and the middle two digits represent red The color is green, and the last two digits represent blue.
Click a color name or hexadecimal value to view the background colors that match different text colors.
A few years ago, when most computers supported only 256 colors, a set of 216 Web-safe colors was proposed as a Web standard. The reason for this is that Microsoft and Mac operating systems use 40 different reserved fixed system colors (approximately 20 each).
We're not sure how meaningful this is nowadays, as more and more computers are capable of processing millions of colors, but the choice is yours.
Initially, 216 cross-platform web-safe colors were used to ensure that all computers could display all colors correctly when using a 256-color palette.
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