The spec language "SHOULD" is not same as "MUST" at all.
No, but in practice all major browsers (Firefox, Chrome, IE, Opera and Safari) do so. And it's not like the implementations of JS and its APIs never differ.
> The spec language "SHOULD" is not same as "MUST" at all.
There are edge case clients that would need to contravene this. Most of those clients don't support JavaScript (or in many cases video) in a meaningful way, making the whole thing moot.
> Also, a tiny bit of JS and no ajax can solve that easily.
No disagreement from me that JS solves these issues.