ok i asked host about override and they said

This AllowOverride directive is not enabled in our shared servers for security reasons. Which means that any directive which has a .htaccess file will be ignored by our system.

This sounds bad... does it mean that I can't run Silverstipe?

Correct. I would find a better host. If they disable this you can run SS without mod_rewrite but knowing hosts who do this you are likely to run into other issues. I am pretty sure if you have 2.3.2 you should be given an option to not install with mod_rewrite

they say in the hosting support datatbase that mod rewrite is fine, but theyre saying override isnt?? do i only need the override for mod re-write?

if i install without mod rewrite i get dirty urls right?

I have installed silverstripe 2.4 and uploaded my allfiles and live went well.
After couple of days I changed the .htaccess file in my ss root folder.(just i donwloaded file from webhost and removed that and placed the same file by adding one line to it.)

here is the change RewriteRule .* sapphire/main.php?url=%1&%{QUERY_STRING} [L] ,
instead of sapphire/main , i replaced /index.php.

Now I am getting mysitename.org but all other home aboutus pages getting blank though I reuploaded original .htaccess file.

### SILVERSTRIPE START ###
<Files *.ss>
Order deny,allow
Deny from all
Allow from 127.0.0.1
</Files>

<Files web.config>
Order deny,allow
Deny from all
</Files>

ErrorDocument 404 /assets/error-404.html
ErrorDocument 500 /assets/error-500.html

<IfModule mod_alias.c>
RedirectMatch 403 /silverstripe-cache(/|$)
</IfModule>

<IfModule mod_rewrite.c>
RewriteEngine On
RewriteCond %{REQUEST_URI} ^(.*)$
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule .* sapphire/main.php?url=%1&%{QUERY_STRING} [L]
</IfModule>
### SILVERSTRIPE END ###

i have searched all and tried all possilibilities.plz let someone give directions to fix.