> For the complete documentation index, see [llms.txt](https://educacion.gitbook.io/programacion/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://educacion.gitbook.io/programacion/pila.md). # pila ## HTML ### HTML Preprocessor #### About HTML Preprocessors HTML preprocessors can make writing HTML more powerful or convenient. For instance, Markdown is designed to be easier to write and read for text documents and you could write a loop in Pug. [Learn more](https://blog.codepen.io/documentation/editor/using-html-preprocessors/) · [Versions](https://codepen.io/versions/) * None * Haml * Markdown * Slim * Pug ### Add Class(es) to `` #### Adding Classes In CodePen, whatever you write in the HTML editor is what goes within the `` tags in [a basic HTML5 template](https://blog.codepen.io/documentation/features/preview-template/). So you don't have access to higher-up elements like the `` tag. If you want to add classes there that can affect the whole document, this is the place to do it. ### Stuff for `` #### About the `` In CodePen, whatever you write in the HTML editor is what goes within the `` tags in [a basic HTML5 template](https://blog.codepen.io/documentation/features/preview-template/). If you need things in the `` of the document, put that code here. **Insecure Resource** The resource you are linking to is using the 'http' protocol, which may not work when the browser is using https. ↑ Insert the most common viewport meta tag ## CSS ### CSS Preprocessor #### About CSS Preprocessors CSS preprocessors help make authoring CSS easier. All of them offer things like variables and mixins to provide convenient abstractions. [Learn more](https://blog.codepen.io/documentation/editor/using-css-preprocessors/) · [Versions](https://codepen.io/versions/) * None * Less * SCSS * Sass * Stylus * PostCSS [Need an add-on?](#0) #### About CSS Base It's a common practice to apply CSS to a page that styles elements such that they are consistent across all browsers. We offer two of the most popular choices: [normalize.css](http://necolas.github.io/normalize.css/) and a [reset](http://meyerweb.com/eric/tools/css/reset/). Or, choose **Neither** and nothing will be applied. * Normalize * Reset * Neither ### Vendor Prefixing #### About Vendor Prefixing To get the best cross-browser support, it is a common practice to apply vendor prefixes to CSS properties and values that require them to work. For instance `-webkit-` or `-moz-`. We offer two popular choices: [Autoprefixer](https://github.com/postcss/autoprefixer) (which processes your CSS server-side) and [-prefix-free](http://leaverou.github.io/prefixfree/) (which applies prefixes via a script, client-side). * Autoprefixer * Prefixfree * Neither ### Add External Stylesheets/Pens Any URLs added here will be added as ``s in order, and before the CSS in the editor. You can use the CSS from another Pen by using its URL and the proper [URL extension](https://blog.codepen.io/documentation/url-extensions/). #### About External Resources You can apply CSS to your Pen from any stylesheet on the web. Just put a URL to it here and we'll apply it, in the order you have them, before the CSS in the Pen itself. You can also link to another Pen here (use the `.css` [URL Extension](https://blog.codepen.io/documentation/url-extensions/)) and we'll pull the CSS from that Pen and include it. If it's using a *matching* preprocessor, use the appropriate URL Extension and we'll combine the code before preprocessing, so you can use the linked Pen as a true dependency. [Learn more](https://blog.codepen.io/documentation/editor/adding-external-resources/) **Insecure Resource** You are linking to a resource using the non-secure http\:// protocol, which may not work when the browser is using https\:// like CodePen enforces. **URL Extension Required** When linking another Pen as a resource, make sure you use a [URL Extension](https://blog.codepen.io/documentation/url-extensions/) of the type of code you want to link to. Either `.css`, `.js`, or the extension of a matching code processor. \+ add another resource ## JavaScript ### JavaScript Preprocessor #### About JavaScript Preprocessors JavaScript preprocessors can help make authoring JavaScript easier and more convenient. [Learn more](https://blog.codepen.io/documentation/editor/using-js-preprocessors/) · [Versions](https://codepen.io/versions/) * None * Babel * TypeScript * CoffeeScript * LiveScript Babel includes JSX processing. ### Add External Scripts/Pens Any URL's added here will be added as ` ``` --- # Agent Instructions This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com. ## Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://educacion.gitbook.io/programacion/pila.md?ask= ``` The question should be specific, self-contained, and written in natural language. 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