RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*)$ /products.php?brandid=27&pname=$1 [NC]

The above works only for branid=27 and If I include mutilple statements, LIKE

RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*)$ /products.php?brandid=27&pname=$1 [NC]
RewriteRule ^(.*)$ /products.php?brandid=42&pname=$1 [NC]
RewriteRule ^(.*)$ /products.php?brandid=47&pname=$1 [NC]

it will also run for brandid 27,
I tried lots of stuff but wont able to rewrite rules for mutiple brandid.

For Example:
The url http://www.3gphone.in/products.php?brandid=27&pname=Acer redirects http://www.3gphone.in/Acer

RewriteEngine On
RewriteRule ^brandid/([^/]*)/([^/]*)$ /products.php?brandid=$1&pname=$2 [L]

Above code will rewrite

http://www.3gphone.in/brandid/27/Acer

to

http://www.3gphone.in/products.php?brandid=27&pname=Acer

If your coding is fetching list from brandid then you have to pass it in URL.

Thanks for the reply..
Here it is the complete code..

Options +FollowSymLinks
Options +Indexes
RewriteEngine on

RewriteCond %{HTTP_HOST} ^3gphone\.in$ [NC]
RewriteRule ^(.*)$ http://www.3gphone.in/$1 [R=301,L]

RewriteCond %{THE_REQUEST} ^[A-Z]{3,9}\ /.*index\.php\ HTTP/
RewriteRule ^(.*)index\.php$ /$1 [R=301,L]

RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*)$ /products.php?brandid=27&pname=$1 [NC]

But I need like http://www.3gphone.in/Acer not http://www.3gphone.in/brandid/27/Acer. Is it possible ?? and second thing CSS is not working..

No..
If you don't pass both variable you can't use brandid in coding.

There is one option just pass pname(Acer) and on top of page use select query and get brandid from database table having model 'Acer'.

And if you want SEO friendly url then you have to also save seo friendly product name in php. space is not SEO friendly.
http://www.3gphone.in/Lemon IT 20717 should be http://www.3gphone.in/lemon-it-20717

Refere this link http://htmlblog.net/seo-friendly-url-in-php/ for php function.

No..
If you don't pass both variable you can't use brandid in coding.

There is one option just pass pname(Acer) and on top of page use select query and get brandid from database table having model 'Acer'.

And if you want SEO friendly url then you have to also save seo friendly product name in php. space is not SEO friendly.
http://www.3gphone.in/Lemon IT 20717 should be http://www.3gphone.in/lemon-it-20717

Refere this link http://htmlblog.net/seo-friendly-url-in-php/ for php function.

Thanks, Now I understand, but my CSS is not working. What should I Do ??

Can you post live URL that you are referring?