I found the info my self.
WWW Prefix - A definition
The WWW Prefix refers to settings in the Windows
registry, which specify how domain names beginning
with 'www' are prefixed. By default, the 'www' prefix is
set to '
http://' and if your computer has the default
settings you can see that domain names entered in the
Internet Explorer address field beginning with 'www' are
prefixed with '
http://'. For example, if you
enter '
www.kephyr.com' in your Internet Explorer browser
it will be replaced with the '
http://www.kephyr.com/' URL.
This setting in the registry can be used for both good
and bad and many browser hijackers employ this to
redirect web traffic through their web site where they
can open pop-up windows or show other types of
advertisements and then redirect you to the site you were
going to in the first place. For example,
CoolWebSearch.ehttp utilize this technique to
prefix '
http://ehttp.cc/?' to domain names beginning
with 'www' and '
www.'. When you enter
www.kephyr.com in
your browser, you end up at '
http://ehttp.cc/?
www.kephyr.com' for a fraction of a second and then they
redirect you to '
http://www.kephyr.com/'.
The WWW prefix is located in the registry
under 'HKEY_LOCAL_MACHINE \ SOFTWARE \ Microsoft \
Windows \ CurrentVersion \ URL \ Prefixes \' where also
other prefixes can be specified. On a Windows XP Home
machine with default settings there are prefixes for
domain names beginning with the following: ftp, gopher,
home, mosaic and www.
Reset the WWW prefix manually
To reset the WWW prefix settings, follow the instructions
below, which includes minor modifications to the
registry.
Start the registry editor. This is done by clicking Start
then Run. (The Run dialog will appear.) Type regedit and
click OK. (The registry editor will open.)
Browse to the key:
'HKEY_LOCAL_MACHINE \ SOFTWARE \ Microsoft \ Windows \
CurrentVersion \ URL \ Prefixes \'. If this registry key
does not exist, the web browser will use the Default
Prefix.
In the right pane, right-click the 'www' value and modify
its data to '
http://'
In the right pane, delete the value called '
www.', if it
exists.
Exit the registry editor.
Close all Internet Explorer browsers.
Your browser should now have the default WWW prefix, and
you can verify this by entering
www.kephyr.com in the
Internet Explorer address field. The domain name should
be replaced with the
http://www.kephyr.com/ URL.
