Questions about programming related to HTML/CSS/etc are off-topic, as are almost all other programming questions (with the notable exception of scripting languages: batch/vbs/powershell/bash/etc).

Questions about software that facilitates programming (webservers/deamons/IDEs/compilers/etc) are on-topic.

Your question is on-topic, since it's not about programming and the answer is to install webserver software.

Please take a look at this page to learn what is on-topic and what isn't.

Neither of the following questions are on-topic on Super User:

1. Is it possible to write other HTML versions in the same page?
2. How do I change my HTML version, and what determines it?

They are about programming, not software of hardware. Please ask on Stack Overflow instead, after checking and making sure no duplicates exist. Also, don't ask if a simple web search answers the question.

Questions about programming related to HTML/CSS/etc are off-topic, as are almost all other programming questions (with the notable exception of scripting languages: batch/vbs/powershell/bash/etc).

Questions about software that facilitate programming and development (webservers/deamons/IDEs/compilers/etc) are on-topic - just like questions about any other software.

Your question is on-topic, since it's not about programming and the answer is to install webserver software.

Please take a look at this page to learn what is on-topic and what isn't.

Neither of the following questions are on-topic on Super User:

1. Is it possible to write other HTML versions in the same page?
2. How do I change my HTML version, and what determines it?

They are about programming, not software or hardware. Please ask on Stack Overflow instead, after checking and making sure no duplicates exist. Also, don't ask if a simple web search answers the question.

Questions about programming related to HTML/CSS/etc are off-topic, as are almost all other programming questions (with the notable exception of scripting languages: batch/vbs/powershell/bash/etc).

Questions about software that facilitates programming (webservers/deamons/IDEs/compilers) are on-topic.

Your question is on-topic, since it's not about programming and the answer is to install webserver software.

Please take a look at this page to learn what is on-topic and what isn't.

Neither of the following questions are on-topic on Super User:

1. Is it possible to write other HTML versions in the same page?
2. How do I change my HTML version, and what determines it?

They are about programming, not software of hardware. Please ask on Stack Overflow instead, after checking and making sure no duplicates exist. Also, don't ask if a simple web search answers the question.

Questions about programming related to HTML/CSS/etc are off-topic, as are almost all other programming questions (with the notable exception of scripting languages: batch/vbs/powershell/bash/etc).

Questions about software that facilitates programming (webservers/deamons/IDEs/compilers/etc) are on-topic.

Your question is on-topic, since it's not about programming and the answer is to install webserver software.

Please take a look at this page to learn what is on-topic and what isn't.

Neither of the following questions are on-topic on Super User:

1. Is it possible to write other HTML versions in the same page?
2. How do I change my HTML version, and what determines it?

They are about programming, not software of hardware. Please ask on Stack Overflow instead, after checking and making sure no duplicates exist. Also, don't ask if a simple web search answers the question.