CSS Comments

All programming languages ​​allow comments and other tips to help understand the meaning of the code. Not all CSS code is as clear as font-size: 20px, so some snippets can benefit from adding comments or other prompts near them. Here is an example:

.cf {
  zoom: 1; /* 用于IE6和IE7 */
}

The comment in this line of code is the part "for IE6 and IE7" which has a leading backslash followed by an asterisk, and the asterisk and backslash at the end recognize it. We can add as many such comments to a style sheet, and using CSS comments to help identify parts of any style sheet that may be difficult to see at a glance is a good practice. By making style sheets easier to read with CSS annotations, CSS will be easier to maintain in the future. CSS comments can span multiple lines if needed. Everything between the start and end comment characters will be ignored by the browser, and the comment characters themselves will be ignored. Therefore, you often see the following in your CSS file:

/***************************
****************************
这些是
页眉部分的样式
****************************
***************************/

Note that in this example, I not only included the start and end asterisk and backslash characters, but also added some extra asterisk characters that span multiple lines. This makes it easy to find comments when scrolling through CSS files. Adding such section titles in CSS helps organize them into easy-to-read related code blocks. Unfortunately, CSS does not have an easy way to render valid single-line comments that use only the starting comment character combination. For example, in JavaScript, you can comment out a line of code like this:

// 这是一个JavaScript注释

This is useful in JavaScript because it can easily invalidate the entire line of code or add useful comments with just two characters (backslash). But in CSS, both the start and end characters must be used to specify the boundaries of any comments. However, for quick temporary fixes, a pseudo-CSS annotation can be created by applying the CSS error principle we discussed in the previous section. Suppose we have the following CSS:

.center-global {
  max-width: 1020px;
  margin: 0 auto;
}

and suppose we want to temporarily delete the first line (max-width declaration). We can do this:

.center-global {
  /* max-width: 1020px; */
  margin: 0 auto;
}

This works fine, but a faster way is to simply place some random characters at the beginning of the line, like so:

.center-global {
  AAAAmax-width: 1020px;
  margin: 0 auto;
}

It's fast and efficient, but never keep such CSS on the event website. It is not a valid CSS and should only be used for rapid debugging in development.

FAQs about CSS Comments (FAQ)

What is the purpose of using CSS annotations?

Annotations in CSS are used for a variety of reasons. They can be used to explain the purpose of a specific code segment, making it easier for others (or even later themselves) to understand the role of the code. Comments can also be used to temporarily disable the code snippet during debugging without removing it. This is especially useful when testing different styles or layouts.

How to write comments in CSS?

In CSS, comments are written by enclosing text between /* and */. For example, /*这是一个注释*/. Everything between these symbols will be ignored by the browser, allowing you to write comments or temporarily disable snippets.

Can I use CSS comments to disable code snippets?

Yes, you can use CSS comments to temporarily disable the snippet. This can be useful when you debug or test different styles. To do this, just enclose the code segment you want to disable between /* and */. For example, /* p { color: red; } */. The browser will ignore everything between these symbols.

Are there different types of comments in CSS?

No, there is only one type of comment in CSS, which is written by enclosing text between /* and */. However, you can use comments in different ways, such as interpreting code, disabling code, or separating code segments.

Can I use CSS comments to separate code segments?

Yes, you can use CSS annotations to separate and organize code snippets. This can make your code easier to read and understand. For example, you can use comments to mark different parts of a style sheet, such as /* 页眉样式 */, /* 主要内容样式 */, and /* 页脚样式 */.

Can comments in CSS span multiple lines?

Yes, comments in CSS can span multiple lines. Everything between /* and */ will be ignored by the browser, no matter how many rows it spans. This can be useful when you need to write longer explanations or disable larger snippets.

Can I nest comments in CSS?

No, you cannot nest comments in CSS. If you try to nest comments, the browser interprets the end of the first comment as the end of the entire comment, which can lead to unexpected results. If you need to write a comment in one comment, you should end the first comment, write a second comment, and then start a new comment.

Will comments in CSS affect the performance of the website?

No, comments in CSS will not affect the performance of the website. The browser simply ignores everything between /* and */, so it doesn't affect how CSS is processed or how the website is rendered.

Can I use CSS annotations to create a to-do list?

Yes, you can use CSS annotations to create a to-do list. This can be a useful way to track changes you need to make or features you want to add. For example, you can write comments like /* TODO：为新窗口小部件添加样式 */.

Can website visitors see the comments in CSS?

No, website visitors cannot see the comments in CSS. They are only visible in the source code and can be viewed by right-clicking on the web page and selecting "View page source code" or "Check". However, it is worth noting that anyone who looks at the source code will be able to see the comments, so you should avoid including sensitive information in the comments.

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