I was sent a question regarding how to open up web-pages in code. After all, the D& specifically states that it can open up a web-page, so it's not easy to know that there is a universal function. He it is though. I hope that you who asked the question feels satisfied. As quoted from the manual:
execute_program(prog,arg,wait) Executes program prog with arguments arg. wait indicates whether to wait for finishing.
execute_shell(prog,arg) Executes the program (or file) in the shell.

That is not all from the manual though. Look up the function and you shall find even more useful information. Indeed I recommend you to read it all, since execute_shell and execute_prgoram can be used for so much more than just opening up a web-page.