There is not default value of HTML src attribute. Its value should be a meaningful substitute for the image. These are full name, email, and password. Supported doctypes
src and srcset New in HTML5 is an image attribute named srcset.
Relative URLs. CSP 3.0 allows it in the case of script-src for external scripts. The src attribute can be used on the following elements: An HTML form with an image that represents the submit button: An audio player with two source files. Example of HTML src attribute with img element, View this example in a separate browser window, Example of HTML src attribute with script element, Example of HTML src attribute with input element, Example of HTML src attribute with frame element, Example of HTML src attribute with iframe element, Previous: HTML span attribute