CSS web page layout misalignment: CSS width calculation-CSS Tutorial-php.cn

CSS web page layout misalignment: CSS width calculation

高洛峰

Release： 2016-10-13 14:13:40

Original

1459 people have browsed it

Why Calculate Width
Calculating the pixel width of web pages is for the neatness and compatibility of CSS web page layout. It is common for us to calculate the width of the entire page when we lay out the left and right structural web pages or use padding and margin layout. If we do not calculate the width, whether the width is too large or too small, misalignment problems will occur.

How to calculate CSS width
Example 1: We calculate the layout style of a left and right structure.
If the total width is 400px, then the sum of the left and right should be less than 400px, then we may have 300px on the left and 100px on the right
Correct code:

<!DOCTYPE html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>左右结构宽度计算www.webjx.com</title>
<style type="text/css">
.webjxcom{width:400px;}
.zuo{ float:left; width:300px; background:#CCC;}
.you{ float:right; width:100px; background:#999}
</style>
</head>
<body>
<div class="webjxcom">
<div class="zuo">左边300px</div>
<div class="you">右边100px</div>
</div>
</body>
</html>

Copy after login

The above is the correct total width of the left and right structures, which is exactly equal to 400px

Error:
If When the total width remains unchanged, the left side is 300px, and the right side is 120px. The total width exceeds 20px. Let’s see what problems will occur. The DIV+CSS code is as follows:

<!DOCTYPE html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>左右结构宽度计算www.webjx.com</title>
<style type="text/css">
.webjxcom{width:400px;}
.zuo{ float:left; width:300px; background:#CCC;}
.you{ float:right; width:120px; background:#999}
</style>
</head>
<body>
<div class="webjxcom">
<div class="zuo">左边300px</div>
<div class="you">右边100px</div>
</div>
</body>
</html>

Copy after login

We can see from the picture above that because the total width The width is about 20px, so the left and right structures cannot be flush, and the right side falls down.
In this way, misalignment compatibility issues arise. Generally, in practice, due to our negligence in calculation, when the difference is small, it is usually 1px-2px, which will not be discovered by us. Therefore, to eliminate misalignment compatibility, we can start with width calculation.

Example 2: There is an example of 1px border in the left and right structure
Generally, there is a 1px border in the left and right structure, and then some borders are added. When we set the left and right structures, we need to calculate the border width and the width of the left and right structures together.
Correct example:
CSS and HTML code are as follows:

<!DOCTYPE html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>左右结构宽度计算www.webjx.com</title>
<style type="text/css">
.webjxcom{width:400px;}
.zuo{ float:left; width:298px; border:1px solid #F00; background:#CCC;}
.you{ float:right; width:98px; background:#999; border:1px solid #F00;}
</style>
</head>
<body>
<div class="webjxcom">
<div class="zuo">左边300px</div>
<div class="you">右边100px</div>
</div>
</body>
</html>

Copy after login

Because the left and right structures have a width of 1px, at this time, each needs to subtract the left and right border width of 2 pixels, so the left side ends up with a width of 298px, and the right side has a width of 98px

If not Subtracting the border will cause the following effects:

DIV+CSS set percentage width calculation
Sometimes we also need to use percentages to calculate width. Usually it is also the total percentage width, which cannot exceed 100%

Pay attention to the summary when calculating CSS width :
Whether it is a left-right structure, a multi-column layout, or a single DIV width layout setting, you need to pay attention to the grasp and calculation of the width, especially when using CSS attributes such as padding, margin, and border. At this time, we all need to set them The occupied width is included in the calculation, and it is important to ensure that the sum of the widths of the same row is less than or equal to the total width. If it is greater than the total width, there will be misalignment compatibility issues. So when there is general misalignment, we can start by calculating the width. Of course, there are many reasons for misalignment. This is also one of the methods to solve the misalignment compatibility problem.