Ethercard.h how add button to webpage

Hello,
I have i2c display, ENC28J60, DHT11 and Arduino Uno.
I have a problem I do not know how to put on a button that would, for example, only patches of saltpeter pin on the 13th. Here’s the code:

#include <EtherCard.h>
static byte mymac[] = { 0x74,0x69,0x69,0x2D,0x30,0x31 };


byte Ethernet::buffer[500];
BufferFiller bfill;

#include <dht11.h>
#include <Wire.h>  

#include <LiquidCrystal_I2C.h>
int piezo = 2;
LiquidCrystal_I2C lcd(0x27, 2, 1, 0, 4, 5, 6, 7, 3, POSITIVE);  // Set the LCD I2C address
dht11 MojeCidlo; 

byte o[8] = {
  B00110,
  B01001,
  B01001,
  B00110,
  B00000,
  B00000,
  B00000,};
int hodnota;  
int vlhkost;
int starahod = 0;
int staravlh = 0;

int horky = 40;
int pred = 0;
bool upozorneni = false;
int predd = 0;
int nejvetcit;
int nejvetsiv;
void setup() 
{
  
  Serial.begin(57600);  

  lcd.begin(16,2);  

   if (ether.begin(sizeof Ethernet::buffer, mymac) == 0) 
    Serial.println(F("Failed to access Ethernet controller"));

  Serial.println(F("Setting up DHCP"));
  if (!ether.dhcpSetup())
    Serial.println(F("DHCP failed"));
  
  ether.printIp("My IP: ", ether.myip);
  ether.printIp("Netmask: ", ether.netmask);
  ether.printIp("GW IP: ", ether.gwip);
  ether.printIp("DNS IP: ", ether.dnsip);

  for(int i = 0; i< 3; i++)
  {
    lcd.backlight();
    delay(250);
    lcd.noBacklight();
    delay(250);
  }
  lcd.backlight(); 
  lcd.createChar(0, o);
  
vypisip("IP:",ether.myip);
delay(1000);
vypisip("Maska:",ether.netmask); 
delay(1000);
vypisip("Brana:",ether.gwip); 
delay(1000); 
vypisip("DNS:",ether.dnsip); 
delay(1000);
vypisip("IP:",ether.myip);
delay(1000);
}


static word homePage() {
  bfill = ether.tcpOffset();
 if(upozorneni == false)
 {
  
  bfill.emit_p(PSTR(
    "HTTP/1.0 200 OK\r\n"
    "Content-Type: text/html\r\n"
    "Pragma: no-cache\r\n"
    "\r\n"
    "<meta http-equiv='refresh' content='1'/>"
    "<title>Teplomer lubinuv pokoj</title>"
    "<h1>Teplomer hlasi:</h1>"
    "<h2>Teplota: $DoC  
 Vlhkost: $D%</h2>
"
    "<h3>Nejvetsi teplota: $DoC  
Nejvetsi vlhkost: $D%</h3>"
   ),
      hodnota, vlhkost,nejvetcit,nejvetsiv);
  
 }
 else if(upozorneni == true)
 {
  bfill.emit_p(PSTR(
    "HTTP/1.0 200 OK\r\n"
    "Content-Type: text/html\r\n"
    "Pragma: no-cache\r\n"
    "\r\n"
    "<meta http-equiv='refresh' content='1'/>"
    "<title>Teplomer lubinuv pokoj</title>"
    "<h1>Teplomer hlasi:</h1>"
    "<h2><font color=\"red\">Teplota: $DoC  </font>
 Vlhkost: $D%</h2>"
    "<h2><font color=\"red\">Je moc horko</font></h2>
"
    "<h3>Nejvetsi teplota: $DoC  
Nejvetsi vlhkost: $D%</h3>"
    ),
      hodnota, vlhkost,nejvetcit,nejvetsiv);
  }

  return bfill.position();
  }
int predy=0;
bool pokra = true;
int predtim=0;
int jedem = 0;
void vypisip(String text ,uint8_t* ippp)
{
  
  lcd.clear();
lcd.setCursor(0,0); 
lcd.print(text);
lcd.setCursor(0,1);
for(uint8_t i = 0;i<4;++i)
{
  lcd.print(ippp[i]);
  if (i < 3)
       lcd.print('.');
  }
 }
 void horko()
{
  
  if ( hodnota > horky){
    tone(piezo, 1500);
    if(upozorneni == false){
      Serial.println("Je moc horko!");
      upozorneni = true;
    }
  }
  if (hodnota < horky) {
    noTone(piezo);
    if(upozorneni == true){
      Serial.println("Uz neni horko.");
      upozorneni = false;
    }
  
  }
  }



void loop()  
{
while(true)
  {
    horko();
    if(hodnota> nejvetcit)
    {
      nejvetcit = hodnota;
     }
     if(vlhkost> nejvetsiv)
    {
      nejvetsiv = vlhkost;
     }
   
  int ted = millis();
  if(ted - predy >= 60000)
  {
    vypisip("IP:",ether.myip);
    pokra = false;
    predy = ted;
    break;
    }
   if(pokra == false)
   {
    if(ted-predtim >= 100)
    {
      jedem ++;
      if(jedem >= 500)
      {
        jedem = 0;
        pokra = true;
        }
      }
    }
  if(ted  -  pred >= 1000 && pokra == true)
  {
  pred = ted;
  MojeCidlo.read(A2);
  hodnota = MojeCidlo.temperature;  
  vlhkost = MojeCidlo.humidity; 
  }
  if(hodnota != starahod || staravlh != vlhkost)
  {
    staravlh = vlhkost;
    starahod = hodnota;
  lcd.clear();
  lcd.setCursor(0,0); 
  lcd.print("Teplota: ");
  if(upozorneni == true)
  {lcd.print("!");}
  lcd.print(hodnota);
  lcd.write(byte(0));
  lcd.print("C");
  if(upozorneni == true)
  {lcd.print("!");}
  lcd.setCursor(0,1);
  lcd.print("Vlhkost: ");
  lcd.print(vlhkost);
  lcd.print("%");
  
  }
  


word len = ether.packetReceive();
  word pos = ether.packetLoop(len);
 ted == millis();
  if (pos)  // check if valid tcp data is received
  {
    if(ted - predd >= 500)
    {
      predd = ted;
    

   ether.httpServerReply(homePage());
    
            
    }
  }
}
}

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