<META> tags are often used to specify keywords and content for a page, but they can also be used for special effects.  For example, this page uses the following code to achieve the transition:

<META HTTP-EQUIV="Page-Enter" CONTENT = "RevealTrans (Duration=4, Transition=23)">
<META HTTP-EQUIV="Page-Exit" CONTENT = "RevealTrans (Duration=4, Transition=23)">