Somewhere around 25 BC Marcus Vitruvius Pollio wrote his "Ten Books on Architecture". The most enduring quote from this work (one that architecture/architectural history students all learn fairly early on) is that:
"Well building hath three conditions: firmness, commodity, and delight."
That is to say, good architecture
- must be strong and durable (firmness)
- must fulfill a purpose (commodity)
- must be beautiful (delight)
According to Vitruvius, any structure that does not meet these basic criteria isn't architecture - it might be sculpture (if it is beautiful but not useful), it might be some form of utilitarian construction (if it is useful but not beautiful), it might be many other things, but it is not architecture.
Of course, in the past 2000 years many building styles and techniques have come and gone and what constitutes "architecture" may look very different, but these three principles stand regardless of the technology.
Web Design hasn't been around as long as Architecture, and although the technology is moving fast, we often don't have the critical distance for any kind of historical/theoretical analysis. But, in this case there's no need to reinvent. Web Design can also make use of these three conditions.
Regardless of the technology that you use to deliver your websites, if it isn't stable and future proof then it is lacking 'firmness'. If a website fulfills no purpose then it is essentially just sculpture. And if your website doesn't have some positive aesthetic qualities, perhaps, as in architecture, we should say that it is not Web Design.