HTML and CSS Reference
In-Depth Information
Most web servers are conigured so that all executable iles must reside in a
cgi-bin or similarly aliased directory. he major exceptions are websites that
use PHP to dynamically generate web pages. PHP iles, which reside in the
document root and subdirectories, are mixtures of executable code and HTML
that are preprocessed on the web server to generate HTML documents. PHP
code is similar to Perl and other CGI languages and, like those languages, has
functions for accessing databases and communicating with other servers.
A web server keeps data about each incoming request and writes this informa-
tion to an access log ile. he server also writes entries into an error log if any
problems are encountered in processing the request. Which items are logged is
conigurable and can difer from one website to the next, but usually some of
the following items are included:
. he IP address or name of the computer the request came from
. he username sent with the request if the resource required
. A time stamp showing the date and time of the request
. he request string with the ilename and the method to use to get it
. A status code indicating the server's success or failure in processing the
. he number of bytes of data returned
. he referring URL, if any, of the request
. he name and version of the browser or user agent that made the request
Here is an example from an Apache access log corresponding to the request
for the ile about.html. he entry would normally be on a single line. I've bro-
ken it into two lines to make it easier to see the diferent parts. he web server
successfully processed the GET request (status = 200) and sent back 12,974
bytes of data to the computer at IP address - [08/Nov/2010:19:47:13 -0400]
"GET /about.html HTTP/1.1" 200 12974
A status code in the 400 or 500 range indicates that an error was encoun-
tered processing the request. In this case, if error logging is enabled for the
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