What Does \'?d=20090107\' in a CSS `` Tag Actually Do?

Unveiling the Mysterious '?' in CSS Links

Upon examining the markup of your favorite website, you stumble upon an intriguing question. Nestled in the tag, a curious string protrudes: "?d=20090107". While it resembles a date, its purpose remains a mystery.

Unveiling the Truth

The "?d=20090107" segment plays a strategic role in ensuring that changes made to the CSS file are disseminated effectively. By adding this unique string to the filename, developers can force browsers to discard cached versions of the CSS file and instead download the updated version.

How It Works

The webserver, upon encountering the "?d=20090107" query parameter, ignores it and serves the file "/Content/all.min.css" as usual. However, browsers, eager to ensure they have the latest version, recognize the altered filename and download it fresh.

Dynamic or Static Content?

While it's conceivable that the CSS is generated dynamically, it's more commonplace to use this idiom to guarantee a reload. The presence of a date in the query parameter further supports the notion that it's a version indicator.

An Automated Solution

Particularly insightful is the excerpt from Podcast 38, which highlights the use of "tags" in the build process. These tags incorporate version numbers into filenames, automating the process of ensuring that browsers always fetch the most current versions of CSS files.

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