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What is quirks mode (compatibility mode)?
sobes.tech AI
Answer from AI
Quirks mode is a rendering mode for web pages where browsers emulate the behavior of older browsers (such as Netscape 4 or Internet Explorer 5) to ensure backward compatibility with web pages written with their quirks and errors in mind.
Main characteristics of quirks mode:
- Non-standard box model: In some browsers in quirks mode, padding and border are included in the total width of the element.
- Non-standard behavior of float and vertical-align: Errors or unpredictable behavior of CSS properties related to alignment and wrapping may occur.
- Differences in font and size handling: CSS rules for determining font sizes and other elements may be applied incorrectly.
- Lack of support for modern standards: Some CSS3 and HTML5 features may be unavailable or function incorrectly.
Browsers switch to quirks mode if the web page does not have a correct doctype or if the doctype is specified in an outdated format. Having a complete and correct DOCTYPE (e.g., <!DOCTYPE html>) switches the browser to standard rendering mode (standards mode).
Example of a correct DOCTYPE for standard mode:
<!DOCTYPE html>