if you install or upgrade APEX your command look like this
sql> @apexins APEX APEX TEMP /i/
and the most common error is that you forgot the trailing slash at the and of image prefix
sql> @apexins APEX APEX TEMP /i
and when you are trying to access to APEX your image, CSS and JavaScript files are disappeared, checking the source code you get something like this
<script src="/ijavascript/apex_builder.js" type="text/javascript">
Probably now you had noticed that the slash is missing after letter i
Solution: Go to your apex install source change working directory to utilities and run reset_image_prefix.sql
sql> @reset_image_prefix.sql
janos ujvari @ 24th november 2009