These are usually called empty tags or single tags. If you make an error when creating a web page in HTML, you will not get a message to tell you. The page will simply look 'wrong' when viewed in the browser. Platform independent HTML is platform independent. This means that you can take a HTML file written on a Mac and run it on a PC or vice versa.
Platform independence is achieved through the use of tags rather than physical styles.
The disadvantage to this is that you can never be quite sure how your document will look to other people viewing your page because THEY have control over how their fonts and styles are displayed, not you. Tags are not case sensitive. If you leave this area blank, the file name is substituted for the title.