I found that in most of the modules contain a index.html with the content
<script>history.go(-1);</script>

However, I found that in c-jay there is a index.html file but contains nothing.

What's the use of the file?

When I click the "Tell a friend" Button in the modules/Themes section in this site. My email client IncrediMail Xe prompt and display the following in the email content field.

Here%20is%20a%20good%20file%20to%20download%20at%20XOOPS%20Official%20Site%3A%20%20http%3A%2F%2Fwww.xoops.org%2Fmodules%2Fmydownloads%2Fsinglefile.php%3Fcid%3D12%26amp%3Blid%3D118

Is it a problem of my OS or my email client?
How can I solve it?

I'm using the version 2.0.4, however, when I opened System admin -> blocks. I don't know how to add system module.

I read a thread here that I may need to include/searchform.php in order to activate the advanced search feature. But, when I added <?php require "include/searchform.php" ?>, my added title is added to top screen but no content. Eventhough I add <?php echo "hello" ?> in the textarea of block, nothing was changed.

I noticed that there is a "system" in module column for system block like user menu, login and main menu. Could you give me more hints to activate the advanced search?