Contribute to Open Source. All three terms (noopener, noreferrer, and nofollow) are values of the rel attribute of the anchor tag in HTML. rdfa defines a processing model for rel values that is incompatible with both previous HTML usage of rel (e.g. The attribute can be used by automated systems, or can be presented to a user in a different way. You get paid, we donate to tech non-profits. Responsive images in Bootstrap with Examples. This element's attributes include the global attributes. Well organized and easy to understand Web building tutorials with lots of examples of how to use HTML, CSS, JavaScript, SQL, PHP, Python, Bootstrap, Java and XML. Documentation for these values is available in the Air Toxics Hot Spots Program Guidance Manual for the Preparation of Health Risk Assessments 2015. How to set the default value for an HTML