I think he means HTML (hypertext markup language).You can do virtually anything with the GIMP on a computer. Although I'm not sure what you mean about hypertext language.
Please note that my only--but very long--experience with the GIMP is on Linux [of course!], but I assume it functions basically the same on other OSes. Also, you should expect something of a learning curve--but once you're good at using it, you can, as I mentioned, do pretty much everything graphics-related with it.
You don't want to do this on your phone, do you?
@Milo Willamson, I'd google "html banner code" as there are different examples that may vary depending on your blog platform .