Send a message from a .htm page to server and show him on LCD

Hello. I'm working on a project and i want to make a server with arduino ethernet shield. I want to put my website on the server and from the contact.htm were i have a box. I want to send any message i want to write there to server and from there to display it on the LCD. Untill now i've make the server with the SD card , the website and now i have problems with this thing. Can anyone help me with how i transfer the message from client to the server and display him on the LCD ?

simple server code with a browser text box, and what is received by the server is printed to the serial monitor.

//zoomkat 4-05-12
//web LED code
//for use with IDE 1.0
//open serial monitor to see what the arduino receives
//use the \ slash to escape the " in the html (or use ') 
//address will look like http://192.168.1.102:84 when submited
//for use with W5100 based ethernet shields
//turns pin 5 on/off

#include <SPI.h>
#include <Ethernet.h>

byte mac[] = { 0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED }; //physical mac address
byte ip[] = { 192, 168, 1, 102 }; // arduino server ip in lan
byte gateway[] = { 192, 168, 1, 1 }; // internet access via router gateway
byte subnet[] = { 255, 255, 255, 0 }; //subnet mask
EthernetServer server(84); //arduino server port

String readString; 

//////////////////////

void setup(){

  pinMode(5, OUTPUT); //pin selected to control
  //start Ethernet
  Ethernet.begin(mac, ip, gateway, subnet);
  server.begin();

  //enable serial data print 
  Serial.begin(9600); 
  Serial.println("servertest1"); // so I can keep track of what is loaded
}

void loop(){
  // Create a client connection
  EthernetClient client = server.available();
  if (client) {
    while (client.connected()) {
      if (client.available()) {
        char c = client.read();

        //read char by char HTTP request
        if (readString.length() < 100) {

          //store characters to string 
          readString += c; 
          Serial.print(c); //print what server receives to serial monitor
        } 

        //if HTTP request has ended
        if (c == '\n') {

          ///////////////
          Serial.println(readString);

          //now output HTML data header

          client.println("HTTP/1.1 200 OK");
          client.println("Content-Type: text/html");
          client.println();

          client.println("<HTML>");
          client.println("<HEAD>");
          client.println("<TITLE>Arduino GET test page</TITLE>");
          client.println("</HEAD>");
          client.println("<BODY>");

          client.println("<H1>HTML form GET example</H1>");

          client.println("<FORM ACTION=\"http://192.168.1.102:84\" method=get >");

          client.println("Pin 5 \"on\" or \"off\": <INPUT TYPE=TEXT NAME=\"LED\" VALUE=\"\" SIZE=\"25\" MAXLENGTH=\"50\">
");

          client.println("<INPUT TYPE=SUBMIT NAME=\"submit\" VALUE=\"Change Pin 5!\">");

          client.println("</FORM>");

          client.println("
");

          client.println("</BODY>");
          client.println("</HTML>");

          delay(1);
          //stopping client
          client.stop();

          /////////////////////
          if(readString.indexOf("on") >0)//checks for on
          {
            digitalWrite(5, HIGH);    // set pin 5 high
            Serial.println("Led On");
          }
          if(readString.indexOf("off") >0)//checks for off
          {
            digitalWrite(5, LOW);    // set pin 5 low
            Serial.println("Led Off");
          }
          //clearing string for next read
          readString="";

        }
      }
    }
  }
}

I understand this . But I want to get the string from my contact.htm where i have the box and the button submit . I want the server take it from there if you understand what i mean.Thanks.