.htm和.html的区别

HTML：
               html was the original extension for HTML pages on Unix Web hosting machines.
HTM：
               htm was created by Windows/DOS because of it's requirement for 3 character extensions.


参考网址 ：http://webdesign.about.com/od/beginningtutorials/a/aa072700a.htm

Filenames

HTML documents use the .htm or. html file extensions, e.g. index.htm or index.html can be used to name your opening page. It also a good idea to use lowercase lettering when naming files. In short, a link specifying a file called History.htm will not work if the file is named history.htm, and a link specifying a file called history.html will not work if the file is named history.htm.

Tips:

• HTML tags should be in Upper Case letters to help differentiate from ordinary text.
• All HTML files in your project should be named with either a .htm or .htmlextension. Do not use both extension types in the same project.
• All HTML file names should be in lower case, with letters and numbers only. Do not use spaces or odd characters (%$£&*).
• Backup your Web Site regularly. If you have WinZip or another compression program, you can achieve this by right-clicking on the folder and choosing "Add to Zip". A few seconds later you have a disaster-management and contingency program.

Note: While there are many excellent HTML editors available, it is useful to know enough HTML to code a document before you begin such an editor. The web pages created by such editors may require some "tweaking" of the HTML code in order to work as you would like them to, and it is much easier to do this if you have a grounding in HTML basics.

看了上面的资料可以明白：

实际上HTM与HTML没有本质意义的区别，HTM只是微软为了满足DOS仅能识别8+3的文件名而自己创建的文件格式，即文件名长度最长为8个字符，扩展名最长为3个字符。

注意：扩展名不同，也即意味着两个文件不同，不是同一个文件，比如index.htm和index.html是两个不同的文件，对应着不同的地址。
 
HTM 为Windows/DOS系统的文件格式，设计目的是为了满足DOS系统的要求；
HTML 为Unix系统的文件格式；

 

目前建议用HTML