You can get great free javascripts on the web. I have a transition on my website. Here's the code (of course substitute your own pictures for the jpg's listed-you don't have to have 5 like the example). I got this from a free javascript site and of course I note the author on my website.
<!-- author David Griffiths, www.demon.co.uk/davidg -->
<TR>
<TD><FONT size=4 color=#FFFF66>text goes here</FONT></TD>
<TD><APPLET CODE="imagefader.class" WIDTH=200 HEIGHT=150>
<PARAM name="demicron" value="www.demicron.se">
<PARAM name="reg" value="A00012">
<PARAM name="maxitems" value="5">
<PARAM name="width" value="200">
<PARAM name="height" value="150">
<PARAM name="bitmap0" value="a00.jpg">
<PARAM name="bitmap1" value="a01.jpg">
<PARAM name="bitmap2" value="a02.jpg">
<PARAM name="bitmap3" value="a03.jpg">
<PARAM name="bitmap4" value="a04.jpg">
<PARAM name="url0" value=" ">
<PARAM name="url1" value=" ">
<PARAM name="url2" value=" ">
<PARAM name="url3" value=" ">
<PARAM name="url4" value=" ">
<PARAM name="step" value="0.05">
<PARAM name="delay" value="20">
<PARAM name="sleeptime" value="2000">
</APPLET></TD>
</TR>
