Firstly, C being provably terminating is a problem dealing with the full body of C programs written in the world. The OP is dealing with their own self-published content. That's a different problem: if your analogy held it would need to be limited to proving that a subset of C programs written by the author terminate.
Secondly, the level of difficulty in making HTML offlineable is many orders of magnitude simpler than your C analogy: there's really no comparison. For the OP we only need to make HTML documents that they have authored themselves offlineable and yet people have written general purpose tools to do this automatically for most webpages. This is not a hard problem.
Secondly, the level of difficulty in making HTML offlineable is many orders of magnitude simpler than your C analogy: there's really no comparison. For the OP we only need to make HTML documents that they have authored themselves offlineable and yet people have written general purpose tools to do this automatically for most webpages. This is not a hard problem.
TL;DR your analogy is absurd.