These server-side techniques can save you and your users both time and space. They increase speed by reducing HTTP requests and shaving 20 to 30 percent off file sizes. They save maintenance costs by including site-wide code snippets. Best of all, these tools can help spice up your site with dynamic or randomized content.
As the name implies, server-side techniques require different levels of server access. Some technologies, such as XSSI, are probably already installed on your server, while others (mod_rewrite, configuration files) may require initial installation by your system administrator. But don't worry; you'll find instructions and sample configuration settings in this chapter. Note that this chapter shows how to configure the Apache server; Microsoft's IIS server can also perform SSI and URL rewrites with ISAPI filters.
Like most things in web design, each of these techniques involves tradeoffs. Each time you shunt more code (long URIs, CGI defaults) and work ([X]SSI) to the server, you make it work a little harder. For high-traffic pages like home pages, the tradeoff favors smaller page size and fewer HTTP requests over any server speed considerations.