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The below script:
Response.Write Request.ServerVariables("PATH_INFO")
Produces: <%Response.Write Request.ServerVariables("PATH_INFO")%>

The below script:
Response.Write Server.MapPath("./")
Produces: <%Response.Write Server.MapPath("./")%> (The current directory)

The below script:
Response.Write Server.MapPath("/")
Produces: <%Response.Write Server.MapPath("/")%> (The root directory of the web site)

AUTH_PASSWORD = <%Response.Write Request.ServerVariables("AUTH_PASSWORD")%>
Returns the value entered in the client's authentication dialog

AUTH_TYPE = <%Response.Write Request.ServerVariables("AUTH_TYPE")%>
The authentication method that the server uses to validate users

AUTH_USER = <%Response.Write Request.ServerVariables("AUTH_USER")%>
Returns the raw authenticated user name

CERT_COOKIE = <%Response.Write Request.ServerVariables("CERT_COOKIE")%>
Returns the unique ID for client certificate as a string

CERT_FLAGS = <%Response.Write Request.ServerVariables("CERT_FLAGS")%>
bit0 is set to 1 if the client certificate is present and bit1 is set to 1 if the cCertification authority of the client certificate is not valid

CERT_ISSUER = <%Response.Write Request.ServerVariables("CERT_ISSUER")%>
Returns the issuer field of the client certificate

CERT_KEYSIZE = <%Response.Write Request.ServerVariables("CERT_KEYSIZE")%>
Returns the number of bits in Secure Sockets Layer connection key size

CERT_SECRETKEYSIZE = <%Response.Write Request.ServerVariables("CERT_SECRETKEYSIZE")%>
Returns the number of bits in server certificate private key

CERT_SERIALNUMBER = <%Response.Write Request.ServerVariables("CERT_SERIALNUMBER")%>
Returns the serial number field of the client certificate

CERT_SERVER_ISSUER = <%Response.Write Request.ServerVariables("CERT_SERVER_ISSUER")%>
Returns the issuer field of the server certificate

CERT_SERVER_SUBJECT = <%Response.Write Request.ServerVariables("CERT_SERVER_SUBJECT")%>
Returns the subject field of the server certificate

CERT_SUBJECT = <%Response.Write Request.ServerVariables("CERT_SUBJECT")%>
Returns the subject field of the client certificate

CONTENT_LENGTH = <%Response.Write Request.ServerVariables("CONTENT_LENGTH")%>
Returns the length of the content as sent by the client

CONTENT_TYPE = <%Response.Write Request.ServerVariables("CONTENT_TYPE")%>
Returns the data type of the content

GATEWAY_INTERFACE = <%Response.Write Request.ServerVariables("GATEWAY_INTERFACE")%>
Returns the revision of the CGI specification used by the server

HTTP_ = <%Response.Write Request.ServerVariables("HTTP_")%>
Returns the value stored in the header HeaderName

HTTP_ACCEPT = <%Response.Write Request.ServerVariables("HTTP_ACCEPT")%>
Returns the value of the Accept header

HTTP_ACCEPT_LANGUAGE = <%Response.Write Request.ServerVariables("HTTP_ACCEPT_LANGUAGE")%>
Returns a string describing the language to use for displaying content

HTTP_COOKIE = <%Response.Write Request.ServerVariables("HTTP_COOKIE")%>
Returns the cookie string included with the request

HTTP_REFERER = <%Response.Write Request.ServerVariables("HTTP_REFERER")%>
Returns a string containing the URL of the page that referred the request to the current page using an tag. If the page is redirected, HTTP_REFERER is empty

HTTP_USER_AGENT = <%Response.Write Request.ServerVariables("HTTP_USER_AGENT")%>
Returns a string describing the browser that sent the request

HTTPS = <%Response.Write Request.ServerVariables("HTTPS")%>
Returns ON if the request came in through secure channel or OFF if the request came in through a non-secure channel

HTTPS_KEYSIZE = <%Response.Write Request.ServerVariables("HTTPS_KEYSIZE")%>
Returns the number of bits in Secure Sockets Layer connection key size

HTTPS_SECRETKEYSIZE = <%Response.Write Request.ServerVariables("HTTPS_SECRETKEYSIZE")%>
Returns the number of bits in server certificate private key

HTTPS_SERVER_ISSUER = <%Response.Write Request.ServerVariables("HTTPS_SERVER_ISSUER")%>
Returns the issuer field of the server certificate

HTTPS_SERVER_SUBJECT = <%Response.Write Request.ServerVariables("HTTPS_SERVER_SUBJECT")%>
Returns the subject field of the server certificate

INSTANCE_ID = <%Response.Write Request.ServerVariables("INSTANCE_ID")%>
The ID for the IIS instance in text format

INSTANCE_META_PATH = <%Response.Write Request.ServerVariables("INSTANCE_META_PATH")%>
The meta base path for the instance of IIS that responds to the request

LOCAL_ADDR = <%Response.Write Request.ServerVariables("LOCAL_ADDR")%>
Returns the server address on which the request came in

LOGON_USER = <%Response.Write Request.ServerVariables("LOGON_USER")%>
Returns the Windows account that the user is logged into

PATH_INFO = <%Response.Write Request.ServerVariables("PATH_INFO")%>
Returns extra path information as given by the client

PATH_TRANSLATED = <%Response.Write Request.ServerVariables("PATH_TRANSLATED")%>
A translated version of PATH_INFO that takes the path and performs any necessary virtual-to-physical mapping

QUERY_STRING = <%Response.Write Request.ServerVariables("QUERY_STRING")%>
Returns the query information stored in the string following the question mark (?) in the HTTP request

REMOTE_ADDR = <%Response.Write Request.ServerVariables("REMOTE_ADDR")%>
Returns the IP address of the remote host making the request

REMOTE_HOST = <%Response.Write Request.ServerVariables("REMOTE_HOST")%>
Returns the name of the host making the request

REMOTE_USER = <%Response.Write Request.ServerVariables("REMOTE_USER")%>
Returns an unmapped user-name string sent in by the user

REQUEST_METHOD = <%Response.Write Request.ServerVariables("REQUEST_METHOD")%>
Returns the method used to make the request

SCRIPT_NAME = <%Response.Write Request.ServerVariables("SCRIPT_NAME")%>
Returns a virtual path to the script being executed

SERVER_NAME = <%Response.Write Request.ServerVariables("SERVER_NAME")%>
Returns the server's host name, DNS alias, or IP address as it would appear in self-referencing URLs

SERVER_PORT = <%Response.Write Request.ServerVariables("SERVER_PORT")%>
Returns the port number to which the request was sent

SERVER_PORT_SECURE = <%Response.Write Request.ServerVariables("SERVER_PORT_SECURE")%>
Returns a string that contains 0 or 1. If the request is being handled on the secure port, it will be 1. Otherwise, it will be 0

SERVER_PROTOCOL = <%Response.Write Request.ServerVariables("SERVER_PROTOCOL")%>
Returns the name and revision of the request information protocol

SERVER_SOFTWARE = <%Response.Write Request.ServerVariables("SERVER_SOFTWARE")%>
Returns the name and version of the server software that answers the request and runs the gateway

URL = <%Response.Write Request.ServerVariables("URL")%>
Returns the base portion of the URL

(Reference: http://www.w3schools.com/asp/coll_servervariables.asp)