Why calculate the width
Calculating the pixel width of the web page is to CSSThe web page layout is neat and compatible. 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, margin layout. If we do not calculate the width, no matter 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:
100px on the right
<head>
< p class="zuo">300px on the left
The above is the correct total width of the left and right structures, which is exactly equal to 400px
Error:
If we keep the total width unchanged, the left side is 300px, and The right side is 120px, so the total width exceeds 20px. Let’s see what problems will occur. The p+CSS code is as follows:
< p class="zuo">300px on the left
100px on the right
We can see from the picture above that because the total width is about 20px, 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, the difference is usually 1px-2px when the difference is small, which will not be discovered by us. Therefore, to eliminate misalignment compatibility, we can start with width calculation.
Example 2: There is a 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 match the border width with the width of the left and right structures. calculated together.
Correct example:
CSS and html code is as follows:
300px on the left
100px on the right
