Do hydrogen halides (HX) form strong or weak acids?
No, it can’t be generalised. Amongst the haloacids, only $\ce{HF}$ is weak.

Acid strength can be determined by the stability of the conjugate base (for most acids, the conjugate base is what you get when you remove $\ce{H+}$ from the acid). In this case the conjugate bases are the halides.

As the size of the halide ion increases, the charge is dispersed over a larger volume, and thus the ion is more stable. In this manner, one can say that the order of acid strengths is $\ce{HF&lt;HCl&lt;HBr&lt;HI}$ (I’m not considering the radioactive ones here; they fit in the same trend though).

$\ce{HCl, HBr, HI}$ are all strong acids. $\ce{HCl}$ has a $\mathrm{p}K_\text{a}$ of −7 (the smaller the $\mathrm{p}K_\text{a}$ is, the more acidic it is), $\ce{HBr}$ is approximately −9, and $\ce{HI}$ is also approx −9.

On the other hand, $\ce{HF}$ is 3.2. The $\ce{H-F}$ bond is pretty strong, so it has a smaller tendency to dissociate—making it a weak acid (not to say that it isn’t dangerous).