You do realize that the most widely used Ruby, PHP, Python, Perl, JavaScript and Java implementations all rely very heavily on C and/or C++ in one way or another, right?
Even when using JRuby, for example, it's still running on a JVM that's very likely implemented using one or both of C and C++.
Don't forget that the major web servers and web browsers are all implemented in C and/or C++, or in one of the many scripting language or other runtime implementations implemented using C and/or C++.
And that's ignoring all of the other infrastructure, like server operating systems, router software, and so forth that's implemented using C, or C++, or both.
Every line of code executing in your non-C or non-C++ web development language of choice likely depends on many thousands of lines of C and C++ code, even as you malign them here.
Yes, of course in the end everything runs on machine code. That does not imply though that it is reasonable to write your web applications in machine code or assembly or C or C++.
I'm not arguing whether or not C++ is actually suitable for web development, I just don't think your line of argumentation makes sense.
The majority of that C and C++ code is hand-written, and not just the output of a compiler or an assembler. They have directly been used to craft some of the most important, and often most difficult to implement, parts of the web application stack.
It's absurd to claim that C and C++ aren't suitable for web development when a huge part of basically every web app today is written in one or both of them. They aren't just suitable for web development; they are critical for it.
You're arguing semantics so let me continue the pattern.
In any non-trivial (jobs/money are on the line), web development != web programming. C/C++ is suitable for web programming, sure, but web DEVELOPMENT is an entirely different matter and is highly dependent on the availability of support, both community and professional, staff, and the competency threshold (or "learning curve") which is the knowledge you need to contribute meaningfully. The latter is one of the most important, especially since the vast majority of C/C++ programmers are not web developers, and doing something wrong in C++ is a lot easier than in memory managed, interpreted languages.
PyPy may someday be a viable replacement for CPython, but that day is not today. The viability becomes much more questionable as more and more of the Python community moves to Python 3, which PyPy basically does not support.
That's not the point. The point is that the argument that modern languages are written in or depend on C/C++ is fallacious: there is no need for C or C++ there, nor is there any technical advantage to their use. CMUCL and SBCL are almost entirely self-hosted, and things like PyPy and JikesRVM stand as strong examples in other languages.
Nobody here has said that C or C++ are absolutely needed. I merely pointed out the reality of the current situation, which is that both C and C++ make up a big part of basically any web app around today, even those written in some other popular languages.
Also note that I referred to "the most widely used" implementations of those languages. Yes, we know that PyPy exists, but CPython is still used far, far more often. Yes, we know about Common Lisp implementations like those you listed, but the reality is that they basically aren't used in practice. PyPy, CMUCL and SBCL are essentially irrelevant when considering the big picture. C and C++ are involved in one way or another in pretty much every other case.
If you refer to the original post in this thread, you will see that it was about the supposed unsuitability of C++ for web development. When we look at the entire picture, however, we do see that such sentiment is quite wrong. C and C++ play an absolutely huge role in modern web development and web applications, regardless of what some people may think.
Even when using JRuby, for example, it's still running on a JVM that's very likely implemented using one or both of C and C++.
Don't forget that the major web servers and web browsers are all implemented in C and/or C++, or in one of the many scripting language or other runtime implementations implemented using C and/or C++.
And that's ignoring all of the other infrastructure, like server operating systems, router software, and so forth that's implemented using C, or C++, or both.
Every line of code executing in your non-C or non-C++ web development language of choice likely depends on many thousands of lines of C and C++ code, even as you malign them here.