100% agree.. but to be a good web designer you need to understand or have an appreciation of html and css. I'm not saying you need to develop 100% in it. or be an excellent hand coder. I'm saying it's simply not good enough to do photoshop mockups anymore as they don't translate to the web.
Go and take a look at web designer jobs on jobs sites and show me one that just want graphic design and photoshop skills.
100% agree back at you.
The best designer/developer relationships I've experienced (I used to be a UI designer for Sega) have been similar to what I imagine a good architect/builder relationship is. There needs to be a healthy overlap of knowledge, a healthy respect for each other's skillset and a very distinct idea of where one's own skills start and end. Each party needs to know when to pull rank, and when to STFU and be told.
I also think there should always be a healthy level of tension. The designer has the brief to answer to, the developer has the technology to answer to. Where these two answers collide is where the work actually happens. If there isn't that tension it's usually because the relationship is uneven, with one side too powerful or complacent.
The trades need each other to flourish, which is why it pains me to have watched so many of my fellow designers get dragged into the world of code where they are simply not cut out to operate.
Not knowing which route to take to get into making websites feels a little bit like saying "I want to make buildings - shall I go down the construction route or the architecture route?". You'd probably know the answer to that long before you needed to settle on one or the other.
So often designers are reluctantly compelled to get into developing because they're worried for their long term employment prospects and hope to future-proof themselves. Actually, in the long term I feel they'll likely find that what they've done is neglected to develop their own skillset in favour of playing distant, third rate catchup to a bunch of dedicated specialist professionals who actually wanted to do that job from the start and weren't distracted by trying to do somebody else's entirely different job as well as their own.
Unfortunately, at industry level that desirable tension I spoke of above is undermined by the sheer disposability of designers. We're ten-a-penny. If you don't want to learn how to be a coder as well as a designer, somebody else will.
It's a shame. In this buyers market where designers are plentiful, the best designers are in theory those few who actually have jobs. And it is they who are being dragged into code for fear of losing them. So the industry compromises many of its best design minds and loses them to the lower echelons of development, which inadvertently lowers the average ability within development accordingly. Nobody comes out of that well.
I've done it both ways. I know which way I found more rewarding, more productive and more profitable.