Apache Guide: Advanced SSI Techniques Page 2

Not that I have anything against IE on Macs–I just struggled for a few
hours last week trying to get some JavaScript working on IE on a Mac, when it
was working everywhere else. The above was the interim workaround.

Any other variable (either ones that you define, or normal enviroment
variables) can be used in conditional statements. With Apache’s ability to set
environment variables with the SetEnvIf directives, and other
related directives, this functionality can let you do some pretty involved
dynamic stuff without ever resorting to CGI.

Conclusion

SSI is certainly not a replacement for CGI, or other technologies used for
generating dynamic web pages. But it is certainly a great way to add small
amounts of dynamic content to pages, without doing a lot of extra work.

See the docs on mod_include for more information on using SSI.