Your documents should be written to a basic html standard and thus viewable by the widest possible audience. In addition, the tags may be affected by the defaults set on your computer when you create the document and on the client computer when the user views the document. The format of your text is not governed by the codes generated through keyboard commands. In other words, hitting return will not space lines in an html document. All formatting must be done through the use of standard tags that are understood by the client's browser.
Most tags comes in pairs to indicate the beginning of the format and the end of the format.
Many people are careless with the end tags and may not include them. This is not a good habit to develop for a couple of reasons. Second, a newer form of markup language , XML, is currently making great strides in the web world and gaining in popularity. XML requires that tags opened must be closed. More information on various tags and how they work can be found in Web Creation Resources .