Web debugging help needed

[chebe]

There is a website that annoys the heck out of me. On the front page there is an ajax powered menu, your from and to destinations, you click a button, and it returns the rail timetable. Except, it doesn't do that for me on Fedora. It works for Ubuntu and Debian users, it works fine in Firefox on Windows. It just doesn't work on Fedora. I opened up the Net panel on Firebug, and saw that there are two requests that never receive responses;

GET http://uk1.siteimprove.com/image.aspx?ourl=javascript%3AGo%28%29&ref=http%3A//irishrail.ie/home/&autoonclick=1&rn=65329

POST http://irishrail.ie/your_journey/timetables_junction1.asp?(parameters_removed)


The first seems to be 1x1 pixel images, so a visitor counter? Although Google Analytics is also being used. Sometimes it doesn't even get to sending the second request. Anyone have some suggestions on what I can do to investigate this further?

Comments

[vatine]

I would probably whip me out a packet sniffer, set it to capture anything to/from the siteimprove.com site (initially, as I have a gut feeling that's where the problem is) and look through the packet trace to see if I see anything suspicions (NAKs, lack of ACKs, not-full-HTTP-responses, that sort of thing).

I suspect Ethereal is a decent one, though you MAY be better off doing the capture with tcpdump (you need root privs, so the lack of a GUI library is a good thing). tcpdump -w /tmp/packetdumpfile.pcap host the.ip.address , then use Etehreal to analyze it. There is a few 'discover odd things in my trace' functions on one of the menus (the 'Expert Infos' choie, towards the bottom of one of them, do not remember the exact place) that can be quite helpful.

But, I spent more than a few years as a network engineer, so I tend to start from the IP layer if it makes half-way sense.

[luguvalium]

I concur - always capture with tcpdump as root, then analyze off-line with Wireshark (Etheral's new name) with a non-root account.

Ratproxy may also show interesting things.

[vatine]

Ah, yes, I was trying to remember if I was writing the old or the new name. Thank you.