i tried the tip

In an .htaccess file in the theme directory or in /themes (so it covers all themes) put:
< Files ~ "theme.html">
Order allow,deny
Deny from all
< /Files>


Now my site IS BROKEN , the site not display my theme,
how i can fix the problem, delete the .htaccess file??
plz urgent help

is a live site.

Solved!

solution, delete the .htaccess file.
A tip for other users with problems for deleting the .htaccess file
:
Note that you may not see .htaccess files in directories when using some FTP clients such as WS_FTP Pro.
Click Connect and then select the site you wish to modify and click on Properties. Select the Startup tab and then enter the two characters -a in the Remote File Mask box. Finally, click OK to confirm the change.
The next time you make an FTP connection to your account you will be able to see a number of hidden files which were not visible before.

grettings