> The result was a completely unusable site: the middle half was in-viewport (good), the right quarter was accessible by scrolling (poor), but the left quarter could not be accessed at all (abject failure).
This is the limitation that browsers/css impose for a rather arbutrary reason [1]
There's nothing preventing the browser from scrolling in any direction.
[1] It's not arbitrary, of course. But almost all these quirks stem from the fact that browers were made to display text and images in a single rendering pass. That's why even in 2025 the article talking about constraints talks about these things as self-evident good defaults with no alternatives:
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If text is centered inside a box too small to contain it, we don't want it spilling out the left edge (it might go off-screen, where the user cannot scroll); left-aligning ensures it only spills out on the right.
That's a funky quirk but also, you may have never noticed it and if you did this edge case probably was better than what the layout would have been. Meaning, actually, building this edge case into the definition of text-align was a smart choice by the CSS designers.
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It was a smart choice for 1995-1999. It's now codified and cannot be changed, but it doesn't mean it's a good choice now, or that it's even an edge case.