Note: This page is primarily geared towards users of the Apache family of web servers. If you are using Netscape Server or IIS, you will need to check their documentation for the their solutions. Users of Stronghold and other Apache offspring should be okay.

This allows you to present your content in a way that is not dependant on JavaScript being enabled, or having people look at your source code to see what the other guy sees!

This is a major benefit to many hosted people that have SSI, but not CGI scripting.

The basis of the this little bit of magic is the ability to use good old IF logic.

Introducing the Basic IF - ELSE - ENDIF
If you have never worked with a programming language before, this may at first appear to be somewhat strange. If you know the slightest drop of any language, you will be able to pick this up in just a few minutes. Once you get the hang of it, you will wonder how you ever lived without it.

The most simple example involves testing to see if some condition is TRUE or FALSE and then acting on it. Consider the following statement:

You are not using an MSIE Browser

Hi! You are using CCBot/1.0 (+http://www.commoncrawl.org/bot.html)

<!--#if expr="${HTTP_USER_AGENT} = /MSIE/" -->
  <B>You are using some kind of MSIE Browser</B><BR>
 <!--#else -->
  <B>You are not using an MSIE Browser</B><BR>
<!--#endif -->

NOTE: The placement of spaces (or lack of them) is critical to making this work. Please look at the code carefully!

Hmmm... If the client is using a browser that contains MSIE in its description, let me say so, else let me say something else.

It is not necessary to use an else, but normally you will to handle exceptions- cases that do not fall into one of your tests.

Using IF - ELSE Logic To Do Even More.
Now put on your thinking cap and consider that you not only can stick HTML in your logic, but also any other type of SSI directive that you could want. Getting some ideas yet? Look at this example.

<!--#if expr="${HTTP_USER_AGENT} = /MSIE/" -->
  <!--#include file="file1.txt" -->
 <!--#else -->
  <!--#include file="file2.txt" -->
<!--#endif -->

Results in the following:

This is text that is contained in file2.txt
I guess you are not using MSIE!

What IS This EXPR Thing?
The expr is a unix'ism. What you need to know for now is this: If what is between the quote marks is TRUE, then what follows the if is done, else it is not.

You can also test for something NOT being TRUE and then acting on it. Just replace add an exclamation (!) mark before the equal (=) sign in your test.

<!--#if expr="${HTTP_USER_AGENT} != /MSIE/" -->

What About The /Stuff/ Between The Slashes
In our expr tests so far, we have been doing what is called pattern matching. The rules used are the same as those employed by the unix egrep utility, and are also referred to as regular expressions. To say the least, learning regular expressions is important, but for our purposes, we will stick to simple matches.