With most scripts you can use HTML even though the extension may not "say" it directly. The most common ones are .php, .php5 .html, .htm, .html5, .html4 .. the lower you go the more outdated the code will become if the server even supports it still ..
Some scripts that don't allow HTML are .js, .css etc .. they're mostly plain text file formats.
.htm, .html, .xhtml
cntrl +s .htm
File extensions.
You cannot convert HTML to MP4 due to different extensions. They both are not compatible with each other.
XML
The original extension of a HTML page was .htm because of file name restrictions that limited filetype extensions to 3 characters, today you can use 3 or 4 so either .html or .htm is perfectly fine.
.html is not an image file, so it can't be converted to .jpg unless the .html file has images in it, in which case you would show extensions and then click in the name box and change .html to .jpg
It depends on what editor you are using to open the file. For there are many extensions a web page can be in.
Show extensions and then click in the name box and change .jpg to .html you will then be able to open your image file with your internet browser.
Its .htm or .HTML for an HTML document. They are the same thing. There is also serverside pages that have other extensions that spit out HTML after the server validates it. .php and .aspx
HTTP is not a file, it is a protocol. It therefore does not have an extension. If you mean HTML files, which are web pages, then either htm or html can be used as extensions.
The most common is .html (hypertext mark-up language)