Users of dynamic languages tend to use tests to check for errors that stronger types might catch (like broken links), but I agree having a formal guarantee is a slight advantage, though not specific to Haskell. Golang for example could easily provide similar checking.

The linked website is beautifully done, and the language does look interesting, I just find the hyperbole about static types making websites magically secure a little over-egged - it's still easy to mess up security or create subtle bugs even if you have strong guarantees about some parts of your code at compile time provided by types.