On most sites, unless they are primarily blogs or news, you don't want to show the name of the author and the date last modified. Especially since some content, 'About Us,' for example, is likely to stay the same for some time, and you don't want it to say 2008 in 2011. When you first install Joomla!, the author and the date show up at the top of every article.
To change this - go to content, article manager. On the upper right hand menu, you will see unarchive, archive, publish, unpublish, move, copy, trash, edit, new, parematers, help.
Choose Parameters 
The pop up windows show the Global Configuration options for articles. You can override any of these options on a per article basis. But for now, we are setting up the defaults that will apply site wide.
The settings you will usually change right away are Author Name, Created Date and Time, Modified Date and Time, and Article Rating/Voting.
If you keep the e-mail and pdf icons next to articles, make sure you test on the front end to see that the emails are really being sent and that the pdf output is acceptable to you.
Each article, when you are editing it, also has the same set of parameters available on the right hand side.
If you are using the category blog layout for a menu item (or the section blog layout), you can also change the parameters in the actual menu item, to show the article date and author for all articles that appear under that menu item. This is handy for when your menu item points to a blog set up using the Joomla! core content.
At the bottom of the Global Configuration pop up, you will see options for 'filtering.' This feature was added to Joomla! in 1.5.8. In most cases, you can leave the default options are they are. If you are having various people submit articles on the front end, you may want to add items to the blacklist (the list of what is forbidden) or the whitelist (everything is forbidden except what you specify) for your front end users. If you're having random strangers submit articles as authors, set the author group to 'no html.'
