I have an iframe on a page that I need to initially have a blank src for, as I eventually set the src with javascript.
I had been using a however have encountered an is
As part of the about URI scheme standard, about:blank is probably the best option as it has very good browser support.
about:blank Returns a blank HTML document with the media type text/html and character encoding UTF-8. This is widely used to load blank pages into browsing contexts, such as iframes within HTML, which may then be modified by scripts. You can see further here