Strange output, but why and how to solve it

yes, i know i now placed the string constants between F().

leaving me with these output readings

Sketch uses 17.372 bytes (56%) of program storage space. Maximum is 30.720 bytes.
Global variables use 1.297 bytes (63%) of dynamic memory, leaving 751 bytes for local variables. Maximum is 2.048 bytes.

and this is the final sketch, some more things to do but so far so good.

// Demo using DHCP and DNS to perform a web client request.
// 2011-06-08 <jc@wippler.nl> http://opensource.org/licenses/mit-license.php
#include <EtherCard.h>
#include <OneWire.h>
#include <DallasTemperature.h>
char payload[50];

void(* resetFunc) (void) = 0; //declare reset function @ address 0

// ethernet interface mac address, must be unique on the LAN
// and other stuff used for the network interface
static byte mymac[] = { 0x74,0x69,0x69,0x2D,0x30,0x31 };
byte Ethernet::buffer[700];

char website[] PROGMEM = "82.72.232.147";//destination website

// Stuff used for one wire sensors
// Data wire is plugged into pin 7 on the Arduino
#define ONE_WIRE_BUS 7


// Setup a oneWire instance to communicate with any OneWire devices 
// (not just Maxim/Dallas temperature ICs)
OneWire oneWire(ONE_WIRE_BUS);
DallasTemperature sensors(&oneWire);
  int temp1;
  int temp2;

// Some random stuff used in this program
static uint32_t timer;
byte wd_counter;

// called when the client request is complete
static void my_callback (byte status, word off, word len) {
  Ethernet::buffer[off+300] = 0;
  // get_reply_data gets the data part of the reply and puts it in the line_buf char a
  
  // Controleer of de data juist is ontvangen.
  if (strcmp((const char*) Ethernet::buffer,"HTTP/1.1 200 OK"))
  {
    wd_counter=0;
    Serial.println( F(" recieved ok."));
  } else
  {
    Serial.println( F(" !!! ERROR !!!."));
    Serial.println( F(">>>"));
    Serial.print((const char*) Ethernet::buffer+off);
    Serial.println( F("<<<"));
  }
}

//Setup the board
void setup () {

  
  //Start serial port
  Serial.begin(9600);
  Serial.println( F("\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n"));
  Serial.println( F("\nNANO EMONCMS Temperatuur sender\n\n\n"));
  
  //Start ethernet port
  if (ether.begin(sizeof Ethernet::buffer, mymac,10) == 0) 
    Serial.println(  F("Failed to access Ethernet controller"));
  //Get own ip adress
  if (!ether.dhcpSetup())
    Serial.println( F("DHCP failed"));
  ether.printIp("IP:  ", ether.myip);
  ether.printIp("GW:  ", ether.gwip);  
  ether.printIp("DNS: ", ether.dnsip);  
  //Look ip destination website
  if (!ether.dnsLookup(website))
    Serial.println( F("DNS failed"));
  ether.printIp("SRV: ", ether.hisip);

  // Startup one wire sensors
  sensors.begin();
}


// Main program
void loop () {


  ether.packetLoop(ether.packetReceive());
  
  if (wd_counter>=10) {
    Serial.println( F("Resetting device"));
    resetFunc();
  }
  

  
  
  if (millis() > timer) {
    wd_counter++;
    timer = millis() + 25000;
    Serial.println(" ");
    Serial.print( F("Attempt number "));
    Serial.print(wd_counter);
    Serial.print( F(" of 10, data send to emoncms: "));
    
    sensors.requestTemperatures();
    temp1 = round(sensors.getTempCByIndex(0)*10);
    temp2 = round(sensors.getTempCByIndex(1)*10);      
    
    sprintf(payload,"{Temp_buiten_camping:%d,Temp_binnen_camping:%d}",temp1,temp2);
    Serial.print(payload);
    ether.browseUrl(PSTR("/emoncms/input/post.json?apikey=913f557706d069745bfe8dac70040261&json="), payload, website, my_callback);

  }
}