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In HTML we usually do comments alike:

<!-- Comment here -->

Why is the comment not symmetrical as in:

<!-- Comment here --!>

I'm looking for the historical answer.

Skeen
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2 Answers2

0

Please look into HTML 2.0 RFC here's and interesting part:

To include comments in an HTML document, use a comment declaration. A comment declaration consists of <!' followed by zero or more comments followed by >'. Each comment starts with --' and includes all text up to and including the next occurrence of --'. In a comment declaration, white space is allowed after each comment, but not before the first comment. The entire comment declaration is ignored.

NOTE - Some historical HTML implementations incorrectly consider any `>' character to be the termination of a comment.

For example:

<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">
<HEAD>
<TITLE>HTML Comment Example</TITLE>
<!-- Id: html-sgml.sgm,v 1.5 1995/05/26 21:29:50 connolly Exp  -->
<!-- another -- -- comment -->
<!>
</HEAD>
<BODY>
<p> <!- not a comment, just regular old data characters ->
Community
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h3XXx
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    I don't believe this answer adresses the symmetry that the question is about. Even though it is an interesting answer. – Skeen Apr 11 '17 at 12:14
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Simply put, it's because it's derived from SGML where that used to be the standard

From sitepoint:

The HTML comment looks like this: . It’s derived from SGML, which starts with an <! and ends with an >

This page has quite some information about the history of HTML and SGML

Shogunivar
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  • Interesting, but the question remains as to why SGML decided for a asymmetric comment indicator scheme. – Skeen Apr 11 '17 at 12:17