also, browsers can resize. It's not the server's job
It's the server's job if the user doesn't want to have to download an ultra-high-resolution image over a metered connection. It also used to be the server's job back when web browsers insisted on using nearest neighbor resampling instead of bilinear or bicubic resampling.
We don't have a bandwidth shortage.
You appear not to know what it's like to be stuck on the 10 GB per month cap of wireless (satellite or cellular) home Internet access.
If you know it's a mac or a PC, you know it's got a desktop range of pixels.
But is that 1024 pixels wide with huge distracting white areas on both sides when viewed on a 2560 pixel monitor, or is it 2560 pixels wide with complete inability to see the entire image at once on a 1024 pixel monitor like the one in my laptop?
Likewise any particular smartphone.
A tablet held in landscape orientation runs the same operating system as a smartphone held in portrait orientation, despite the latter having only about one-third the horizontal width.
Don't resize images with the viewport. That's very annoying. They should reflow with the window according to the browser's settings. If you set a constant width, then you're asking for scroll bars if the window can't fit that width.
So what should a designer who doesn't want horizontal scrollbars do?
HTML was intended as the content provider; the browser intended to be the content formatter
And CSS (Cascading Style Sheets) was supposed to be the instructions that the content formatter follows.
using only hints -- lines, paragraphs, font styling, etc. The closer you can get to that in web page design
I imagine that as of 2014, most people would not prefer that most web pages look like Barry T. Smith's MFing Web Site. They would consider the default styling that a browser applies to the MFing Web Site to be unprofessional.
Every time some whackjob decides that menus should drop or windows should open when my mouse pointer crosses some object, I curse.
Every time I run into some page (like liveaquaria.com's) that won't run its cart or checkout through the usual standard ports and protocols
Could you describe what nonstandard "ports and protocols" liveaquaria.com uses? I tried to buy a coral to test what you describe, but it required me to create a username and password before I could check out. Is the need to register before checking out part of the problem you describe? I do know that some manufacturers, such as Games Workshop, have a policy of forbidding online stores from selling their products through a standard shopping cart.