Understanding CSS Specificity, Media Queries, and min-width
When implementing responsive web design using the "mobile first" approach, min-width allows designers to define CSS rules based on device width. However, challenges arise when overwriting CSS values, as the lower min-width may take precedence.
The Issue
An example demonstrates the problem:
@media only screen and (min-width: 600px) { h2 { font-size: 2.2em; } } @media only screen and (min-width: 320px) { h2 { font: normal 1.7em/2.1em Helvetica, sans-serif; } }
Ideally, resolutions above 600px should display an h2 font size of 2.2em. However, the 1.7em declaration takes precedence.
The Resolution
Media queries operate on a specificity hierarchy, where the most specific ruleoverrides those with less specificity. In the example above, the first media query is more specific because it specifies a higher minimum width.
The correct approach is to reorder the media queries so that the more specific rule, which sets a font size of 2.2em, appears last:
@media only screen and (min-width: 320px) { h2 { font: normal 1.7em/2.1em Helvetica, sans-serif; } } @media only screen and (min-width: 600px) { h2 { font-size: 2.2em; } }
This ensures that the desired CSS rule for resolutions above 600px takes effect, even if it has a lower min-width value.
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