When I modify a theme and upload the theme.html file to the theme folder and reload the pages, the pages just don't change! If I change the name of the theme foler, and also change defalt theme in the preference option, it will work. I am just wondering if there's a way that I don't need to change the theme folder name. Thanks a lot!

Go to preferences and check yes on

Update module template .html files from themes/your theme/templates directory?

You won't want to leave it this way though...
for one reason it will send more queries to the db.
but it will do what you want when checking out theme changes.

Quote:

Thank you so much. I didn't notice this in the settings. :)

I'm glad it was helpful =)

sorry for bringing up again this issue. I have the same problem but a little more specific. Let me explain:
I did a clean install of XOOPS built in the Fantastico scripts of my host. Installed all necessary modules and then cloned the site/db to other 4 sites, that differ only in content. The replication went fine and all the sites are fully functional. However for some reason the changes I do to the template will occur only in the original installation. All the cloned sites wouldn't change a thing even if I tried all the tips given under the FAQs.
I played around with enabling changes in the preferences with site on and offline,
used different browsers witha cleaned cache,
played around with permissions, using both a ftp client or the filemanager on cPanel
and more and more..but the damnt theme.html stays the same.
I don't know what changes on the clone sites that i'm missing. Maybe files in template-c dir are making a mess out of it?!

looks like the template_c folder was causing the mess. "Deleting all files within except index.html", surely won't work at least for me. However changing permissions to it (777) and to the template folder did the trick. . Dont forget to chmod back after things will sort out