# HTML ``` ### HTML vs. XHTML Difference In XHTML, attribute minimization is forbidden. If you are writing XHTML-compliant code, the `defer` attribute must be explicitly defined with its value: ```html ``` --- ## Code Example In this example, the script `demo_defer.js` will download in the background while the browser parses the HTML. The script will only execute after the entire DOM tree is fully constructed. ```html

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The content of this page will render without being blocked by the script download.

``` --- ## Script Execution Strategies: `defer` vs. `async` vs. Normal Understanding how the browser handles scripts is essential for web performance optimization. Here is how the three main execution strategies compare: | Strategy | HTML Parsing | Script Download | Script Execution | | :--- | :--- | :--- | :--- | | **Normal** (`