Embed Tag and JavaScript

Hello,
Iam trying to load an applet automatically after a time interval when the user does not respond using the OnLoad function. In the function iam calling from the OnLoad function , i check for navigator and IE Browsers, Where i include the plugin for Java 2 Browser support using document.write property inside the javascript. Every thing works fine in IE. But Netscape gives a javascript ERROR and hangs. Can some one tell the solution ? Can't i use the OnLoad function when i use the EMBED tag.
Thanks,
Raja