This website, CSS Lint, is a tool that helps you improve your CSS code by analyzing it and suggesting potential problems. You can paste your CSS code into the provided space, and the website will run it through its linter. The results will show any errors or potential issues that may be hindering your code's performance or accessibility. 


CSS Lint Online | Css Linter | Css Validator

This website provides a free online HTML validator and linter. It checks HTML files for compliance with W3C standards and assesses code quality against best practices. The validator can identify missing or unbalanced HTML tags, stray characters, duplicate IDs, missing or invalid attributes, and other issues. It supports HTML5, SVG 1.1, MathML 3.0, ITS 2.0, and RDFa Lite 1.1. Users can either copy and paste their HTML code or upload an HTML file. The validator also allows users to choose the file encoding. 


Free Online HTML Validator - FreeFormatter.com

This website, OFOCT.COM, offers an online ePub viewer. Users can drag and drop ePub files, upload them from a URL, or integrate the viewer into their own website using an API. The viewer can also be used to view various other file types, including AI, SVG, PSD, DICOM, TIFF, VSD, CR2, Office files, and more. 
