Server haulting after 4 days

Using Arduino Networking, Protocols, and Devices
2

You can use the progmem macro F() to put static text in program memory like below.

client.println(F("<HTML><HEAD><TITLE>Arduino GET test page</TITLE></HEAD><BODY><H1>Zoomkat's simple Arduino button</H1><a href='/?on''>ON</a>&nbsp;<a href='/?off''>OFF</a></BODY></HTML>"));