Web Front-end
CSS Tutorial
How Does the DOCTYPE Declaration Affect CSS Height Percentage Calculations?
How Does the DOCTYPE Declaration Affect CSS Height Percentage Calculations?
CSS Height Property, Percentage Values, and DOCTYPE
When you specify a height of 100% to your div element, it may not fill the entire page because in standards mode (when the DOCTYPE is included), the browser applies the percentage height relative to the parent element's height. However, if you remove the DOCTYPE, the browser switches to quirks mode and interprets the 100% height relative to the viewport.
Making the Div Fill the Page
To ensure that your div fills the page without removing the DOCTYPE, declare a height on the root element:
html { height: 100%; }Why Removing the DOCTYPE Affects Height Calculation
When the DOCTYPE is removed, the browser switches from standards mode to quirks mode. In quirks mode, percentage heights of child elements are calculated differently:
- Standards mode: If the parent element has a height of auto, percentage heights of child elements are also treated as auto.
- Quirks mode: If the parent element has a height of auto, percentage heights of child elements are measured relative to the viewport.
Since you have not set a height on your div's parent element, the 100% height is measured relative to the viewport in quirks mode, causing the green background to fill the page as expected.
Importance of a DOCTYPE
Using a DOCTYPE is crucial because it ensures that the browser renders your web page in standards mode. This mode follows modern web standards, guaranteeing consistent and reliable rendering across different browsers. Quirks mode, on the other hand, simulates older browsers to accommodate legacy web pages, which can lead to unpredictable and undesired behavior.
Recommended DOCTYPE
For HTML5 documents, the recommended DOCTYPE is simply:
<!DOCTYPE html>
The above is the detailed content of How Does the DOCTYPE Declaration Affect CSS Height Percentage Calculations?. For more information, please follow other related articles on the PHP Chinese website!
Hot AI Tools
Undresser.AI Undress
AI-powered app for creating realistic nude photos
AI Clothes Remover
Online AI tool for removing clothes from photos.
Undress AI Tool
Undress images for free
Clothoff.io
AI clothes remover
Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!
Hot Article
Hot Tools
Notepad++7.3.1
Easy-to-use and free code editor
SublimeText3 Chinese version
Chinese version, very easy to use
Zend Studio 13.0.1
Powerful PHP integrated development environment
Dreamweaver CS6
Visual web development tools
SublimeText3 Mac version
God-level code editing software (SublimeText3)
Hot Topics
1671
14
1428
52
1329
25
1276
29
1256
24
A Comparison of Static Form Providers
Apr 16, 2025 am 11:20 AM
Let’s attempt to coin a term here: "Static Form Provider." You bring your HTML
A Proof of Concept for Making Sass Faster
Apr 16, 2025 am 10:38 AM
At the start of a new project, Sass compilation happens in the blink of an eye. This feels great, especially when it’s paired with Browsersync, which reloads
Weekly Platform News: HTML Loading Attribute, the Main ARIA Specifications, and Moving from iFrame to Shadow DOM
Apr 17, 2025 am 10:55 AM
In this week's roundup of platform news, Chrome introduces a new attribute for loading, accessibility specifications for web developers, and the BBC moves
Some Hands-On with the HTML Dialog Element
Apr 16, 2025 am 11:33 AM
This is me looking at the HTML element for the first time. I've been aware of it for a while, but haven't taken it for a spin yet. It has some pretty cool and
Paperform
Apr 16, 2025 am 11:24 AM
Buy or build is a classic debate in technology. Building things yourself might feel less expensive because there is no line item on your credit card bill, but
Where should 'Subscribe to Podcast' link to?
Apr 16, 2025 pm 12:04 PM
For a while, iTunes was the big dog in podcasting, so if you linked "Subscribe to Podcast" to like:
Weekly Platform News: Text Spacing Bookmarklet, Top-Level Await, New AMP Loading Indicator
Apr 17, 2025 am 11:26 AM
In this week's roundup, a handy bookmarklet for inspecting typography, using await to tinker with how JavaScript modules import one another, plus Facebook's
Options for Hosting Your Own Non-JavaScript-Based Analytics
Apr 15, 2025 am 11:09 AM
There are loads of analytics platforms to help you track visitor and usage data on your sites. Perhaps most notably Google Analytics, which is widely used
