Many times when you are implementing a SharePoint 2007 (MOSS) solution, it turns out that some of the many features that SharePoint provides aren’t needed or wanted. For instance, you might want to hide the default left-side navigation or the My Site link. There is a simple trick for doing this. Rather than removing the placeholder (or its contents) from the master page, simply override the cascading style sheet (CSS) class. For instance, to turn off the left-side navigation, you would use:
This way, the master page element is still there if you decide later that you would like to turn it back on.
Another plug for one of my favorite Web development tools: the Internet Explorer Developer Toolbar (also called the IE DOM Explorer). Using this toolbar, you can select a master page element by clicking on it to see which CSS class is being applied to it easily, rather than opening the master page in SharePoint Designer.