Alt tag refers to the text that is associated with an image. This originated from when web browsers were not universally available as “Graphical Browsers” so the “Alt text” was a description used to describe the image. Now adays it is also used in the “mouseover” text popup that appears when you move your mouse over a graphical image.

The Future of WordPress: Trends and Technologies to Watch
WordPress, the ubiquitous content management system (CMS) powering over 43% of all websites, is far from stagnant. While its core principles of user-friendliness and extensibility