Databases Reference
In-Depth Information
If you drill down into the detail of one of those resources, you can see more details about the request
and response headers, as shown in Figure 1-10.
Figure 1-10.
Viewing response and request header detail
Notice in Figure 1-10 that you can view the handshaking and communication between the browser
and the web server. The request headers are from the browser informing the web server which languages
and encodings it supports; the web server responds with the response headers (and content) to tell the
browser what data is being returned and in what format. The key thing here is to notice in the Request
Headers the line that reads
Accept-Encoding: gzip, deflate
This is the browser telling the web server that it supports compressed data in the response. The
compressed data can be either in the gzip or deflate format (the end results of compression are similar,
but use slightly different methods). The web server can then decide whether to send compressed or the
default uncompressed content, depending on whether the browser supports compression or not. If the
browser does not support compression, it won't send that request header and the web server will send
the regular uncompressed response. In other words, there's little to no downside of enabling
compression on your web server, since any browsers that don't support compression will still have the
uncompressed data sent to them, while browsers that do support compression will benefit from the
compressed version.
In my first topic,
Pro Oracle Application Express
, I went into a lot of detail on installing and
configuring the
mod gzip
module (which is another Apache module) that enables your web server to
provide compressed output. I'm not going to reproduce all the steps here (I'm hoping you already
purchased that topic!), but I do want to show the effects, in case you either didn't buy that topic or
simply skimmed past that bit.
So you've seen how you can examine the web page content using Firebug. Let's look quickly at
another Firefox plug-in that I find extremely useful (bear with me, it is relevant to web server
compression). That plug-in is called
YSlow
and is available from
http://developer.yahoo.com/yslow
. It
was actually developed by Yahoo (hence the Y in
YSlow
) as part of their ongoing development to profile
and optimize the Yahoo websites. What YSlow does is to run a series of checks and rules against your
web page and assign a score against each of those checks. For example, in Figure 1-11 you can see that
