can't connect to webserver through arduino
As you are getting a 404 error, the Arduino must be correctly connected to the network and able to access the web server.

(My best guess, given limited information, is that the web server is using Virtual Hosting and your Arduino is not sending a "Host:" HTTP header).

In order to debug the problem, you need to see what's going on at the network level.
Either, add debugging to your Arduino HTTP library or sniff the network with a PC.

I'd recommend using a PC. Use an ethernet hub (not a switch), or connection share the Arduino through a PC then run WireShark to sniff the network packets. Check that the Arduino really is requesting the page you think it is. Check the response codes coming back.

Recreate the HTTP request on a PC, send exactly the same data - do you get the same 404 response? You can do this with telnet or with a more powerful tool like curl or wget.