HTM and HTML

• HTM files are actually exactly the same as HTML files. Both file extensions refer to a document of Hyper Text Markup Language code. The reason that HTM exists at all is because of the limitations of some software, specifically web development software from Microsoft. It was designed to work with file extensions that were exactly three characters long. The four character ".html" extension was therefore shortened to accommodate the limitation.
  
  

Web Pages

• HTM and HTML files are, put simply, web pages. The consist of code, in the form of simple text characters, designed to be interpreted by a web browser such as Firefox or Internet Explorer. The code in the HTM file tells the browser what to display, where on the screen to display it, what styles and formats to use, where to put images or other media, and so on. When you browse the web, you are mostly looking at HTML and sometimes HTM files.
  
  

Text Only

• The information in an HTM or HTML file is text-only. In other words, the binary data contained in the file represents common text characters, and can therefore be properly read and displayed by any text software. Microsoft Word or OpenOffice.org shouldn't have any problems showing you the contents of an HTM file. If you can't open it in a text editor or you only see a mess of unreadable characters, then the file is likely corrupt or has the wrong file extension.
  
  

Opening HTM Files

• You can open an HTM file with any software capable of opening an HTML file. This includes all web browers, such as Google Chrome, Mozilla Firefox, Microsoft Internet Explorer and Apple Safari. You could also use any text editor, such as Microsoft Notepad or Apple TextEdit, to look at the HTML code itself. And, of course, you can open HTM files with web development software, such as Adobe Dreamweaver.