• Non-standard web development practices, proprietary features, or coding patterns that were specific to Microsoft’s Internet Explorer browser and that diverged from established practices. IEisms include IE-only HTML attributes, CSS properties, JavaScript methods, or rendering behaviors that worked in Internet Explorer but were not supported by other browsers, often requiring developers to write browser-specific workarounds or conditional code. IEisms were a significant source of cross-browser compatibility issues during IE’s dominant years and are now largely considered legacy practices to be avoided in modern web development.

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