Code validation tools:

Markup Validation Service - Free service that checks Web documents in formats like HTML and XHTML for conformance to W3C Recommendations and other standards.

WDG HTML Validator - The WDG Validator will check the syntactical correctness of your HTML to help you produce more accessible Web pages.

CSS Validation Service - Check Cascading Style Sheets (CSS) and (X)HTML documents with style sheets.

RSS Feed Validator - Free Atom & RSS Feed Validator.

W3C Feed Validation Service - Free service that checks the syntax of Atom or RSS feeds.

RSS Validator - Free RSS validator tool.

Redland RSS 1.0 Validator and Viewer - Enter the address of an RSS 1.0 feed into the following form and it will be validated and formatted for display.

Validator for Atom and RSS feeds - This tool provides validation of your Atom and RSS files based on XML schema validation; as not all requirements of appropriate specifications can be expressed in a XML schema, we provide additional checks to insure the
conformance of documents to check to exsting RSS and Atom specifications and standards.

Code validation tools
Check the syntactical correctness of your HTML and CSS to help you produce more accessible web pages. Feed validators provides validation of your Atom and RSS files based on XML schema validation.

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