Thanks for an excellent site! It has been really useful for me!
I have 3 related questions to results I don’t understand.
In the test results below there is a long delay before the page load is finished, but what is causing it? It is just empty space before favicon is finally coming from Cloudfront: http://www.webpagetest.org/result/110914_JZ_1KMAD/3/details/ http://www.webpagetest.org/result/110914_AE_1KMAB/2/details/
Can it be Adsense making the delay? The page is fully cached so it should not have anything to do with the server.
I get results like above quit frequently. Can I do anything about it?
Is that to be expected? I have seen it a few times since I started with CDN two days ago.
Is Amazon Cloudfront a good choice? Will they always speed up the page load or is it sometimes better with CDN and sometimes better without CDN?
It’s hard to say but it could certainly be a “bad ad”, particularly if it is really intermittent. I tried running a bunch of tests and couldn’t get it to happen again so it’s really hard to say. The CPU doesn’t spike to 100% so it’s not a case of javascript running out of control (a common cause for gaps). It could be a flash interaction with IE that doesn’t go well though.
That one looks like the ad possibly did something on a 500ms timer from the flash file which is why there are 2 blocks of activity 0.5 sec apart after the flash file loaded.
No, that’s not good. It could have been cloudfront itself or cloudfront trying to connect to your server. From the looks of the headers, the favicon isn’t explicitly cacheable - you should add expires headers to it so the CDN (and users) can cache it - WebPageTest Test - WebPageTest Details