On purchase orders many art buyers will have the usage rights for print written out and will also use the term "global electronic". This is usually stated instead of "web" because today the reach of digital includes so many different aspects. Global electronic or electronic media can include but is not limited to traditional websites, banner ads, email, mobile media, digital kiosk and billboards, blogs, postcardware, and games. The term can also sometimes include broadcast, for example using the still images in a viral video. It's best to work with the art buyer or client to spell out and clarify the uses of the intended electronic media.
Interactive and electronic costs are all over the board and vary wildly. It's a good idea, just like for print uses, to have possible electronic uses mapped out. If you're unsure, check out PLUS for usage definitions and license suggestions. Good resource communities are ASMP or ASPP.