If you read my previous post on YSlow!, you know we made every attempt to assuage the YSlow! gods appeasing their insatiable appetite for efficiency.

So, we configured our S3 buckets to serve gzipped CSS and JS.

Unfortunately, we didn't account for how horrible the IE browsers are.

We began getting emails from folks in our Bristol offices with screen shots of pages that looked like the CSS hadn't loaded.

We booted up Parallels and had a look, and both IE6 and 7 looked fine to us. So we sent the usual replies: Try clearing your cache, it must be a setting you have on, upgrade your browser, etc, etc.

You see, we don't use PCs and we don't use the network, which just about everyone else in Disney uses. We have clean, unfettered, beautiful access to the Internet, so this problem seemed like it had to be bunk.

But then we started seeing user reports of the same thing. So I got my Google on and started researching gzipping assets and IE. There seemed to be some stuff related, but not a sliver bullet, and nothing that could explain why our IEs were fine and Bristol's weren't.

Then I remembered some of the pure wackiness that we endured on the network when I worked in Bristol. So we blew the dust of a Thinkpad Laptop, which was connected through our network, and brought up Fan Profiles on IE6.

Booyay! It was like National Turn CSS and Javascript Off For A Day, and we were failing miserably at it. Oh, Firefox and Safari and Opera were fine, but that's to be expected.

I didn't really know what to do because we had seen pretty serious page load gains from gzipping our content.

In the end, we decided at least temporarily, to not gzip, so we rolled back, and problem solved.

Interestingly, at the same time, our CNAME request for serving assets through Akamai completed. When I set up the configs for Akamai, I requested that it gzips the content.

So in theory, the content was being gzipped again. Even more interesting, IE on the network still looked fine.

YSlow! was happy. The network was happy. I was suspicious.

Was the content really being gzipped?

I looked around for a while to find out how I could test this. To save you time:

curl -I -v --compressed -A "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1)" http://a0.espn.go.com/javascripts_c/main.js?1210961500

And yes, it was being gzipped.

So for reasons I still don't understand, IE + corporate network + Gzipped content from S3 != E + corporate network + Gzipped content from Akamai, being sourced from S3.