Arduino uno Web server problem

Hi
i have arduino uno
when i upload the code the web server run but when i add more code you can’t open the webserver anymore in the browser but still i can ping it
here the code:
I put login to be able to control if you know another way to login like this one please Help me

#include <String.h>
#include <SPI.h>
#include <Ethernet.h>
byte mac[] = { 0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED }; //physical mac address
byte ip[] = { 192, 168, 1, 102 }; // ip in lan
byte gateway[] = { 192, 168, 1, 1 }; // ip in lan
byte subnet[] = { 255, 255, 255, 0 }; //subnet mask
EthernetServer server(80); //server port
String readString; //string
boolean LED1ON = false; //LED1 status flag
boolean LED2ON = false; //LED2 status flag
boolean LED3ON = false; //LED3 status flag
boolean login=false;
int light = 0; // variabile da calcolare 
int potenvalue = 0;
int servo = 9;
float tempC;
int reading;
int tempPin = 0;
/////////////////////////////////
void setup(){
Ethernet.begin(mac, ip);
login = false;
   pinMode(servo, OUTPUT);
  login=false;
  Serial.begin(9600);
}
void loop(){
    light = digitalRead(A1);
    potenvalue = analogRead(A0);
    
    reading = analogRead(A3);
tempC = reading / 9.31;
/*inizio client*/
EthernetClient client = server.available();
if (client) {
  boolean currentLineIsBlank = true;
  while (client.connected()) {
    if (client.available()) {
      char c = client.read();
        readString.concat(c);
      if (c == '\n' && currentLineIsBlank) {
        // Serial.print(readString);
        if(readString.indexOf("Nome=user&Pwd=user") > 0) {
 
login=true;
         
        }
     
        ////////////////////////////////////////////////////////////////////////////
        
        if(login==true){
        if(readString.indexOf("L=1") > 0) {
                                          // in steps of 1 degree 
    digitalWrite(servo,50);
    
          LED1ON = true;
          }else
          if(readString.indexOf("L=01") > 0) 
          {
                                  
    digitalWrite(servo, 0);         // tell servo to go to position in variable 'pos' 
 
          LED1ON = false;
        }
        ///////////////////////////////////////////////////////////////////
    
        /////////////////////////////////////////////////////////
        if(readString.indexOf("Logout") > 0) {//lets check if LED should be lighted
          //led has to be turned ON
          login=false;
          }      
        } 
        /////////////////////////////////////////////////////
        // INIZIO DICHIARAZIONE PAGINA HTML
        client.println("HTTP/1.1 200 OK");
        client.println("Content-Type: text/html");
        client.println();
        client.print("<html><head><title>Room security system</title><meta http-equiv='Content-Type' content='text/html; charset=iso-8859-1' ><center></head><body>");
       client.println("<h1><center>Welcome to room security system</center></h1><hr />");
        // Finestra di login
        if (login == false) {
          client.println("<h1><center>Please login to control!</center></h1>");
        client.print("<form action='http://192.168.1.102/'><center>");
           client.print("");
        client.print("Username: <input name='Nome' value=''>");
        client.print("Password: <input type='Password' name='Pwd' value=''>");
        client.print("<input type='submit' value=' Login '>");
        client.print("</center><hr /></form><hr />");

        client.print("<marquee behavior='slide' direction='left'  loop='40' >Welcome to room security system website, please login to use this website, project by Zhiran, Thank's for visiting</marquee>");
           
        }
        ////////////////////////////////////////////////////////////////////////////
        if (login==true) { 
        client.println("<h1>Sensors & Light & Alert:</h1><hr />");         //Scrive sul browser il valore del termistore     
        client.print("<p><strong>Potentiometer value:</strong></p>");
client.println(potenvalue);              
client.println("
</p>"); 
  client.print("<p><strong>Room temptreature:</strong></p>");
client.println(tempC); 
client.println("Celsius"); 
client.println("
</p>"); 
        client.print("<p><strong>Light sensor: </strong></p>");
if (light == HIGH) {           // scrive sul web luce se il valore della fotoresistenza è alto           
client.print("<p><strong>There is enough light to see</strong></p>");         }      
else {           // scrive sul web buio se il valore della fotoresistenza è basso           
client.print(" <p><strong>Light level is low, lights are turned on automatically</strong></p>");         } // link per aggiornare pagina e valori 
//////////////////////////////////


        /////////////////////////////////////////////////
client.print("<h2>Refreash sensors: <a href=''>click here</a></h2><hr />");                   
        client.println("<h1>Door control</h1>");
        client.println("
");
        //printing LED status
        ///////////////////////////////////////////////
        client.print("<span>Door state  </span>");
 
          if (LED1ON) {
              client.println("<span style='color:green'>open</span>");
            }
            else
            {
              client.println("<span style='color:grey'>closed</span>");
          }
        client.print("<h2><a href='/?L=1'>open</a> | <a href='/?L=01'>close</a></h2>");
        
        client.println("<hr />");
        
        //Secondo led
         client.println("
");
        //printing LED status
        client.print("<h2><a href='/?Logout'>Logout</a>");
        client.println("<hr />");
        client.print("<span><strong>Project by Zhiran</strong?</span>");
       
        } //chiude if login=true 
        client.println("</center></body></html>");
 
        //clearing string for next read
        readString="";
        //stopping client
        client.stop();
        
 
        } 
    } 
  } 
} 
}

but when i add more code you can’t open the webserver anymore in the browser

Get rid of this, and all uses of the String class:

#include <String.h>

I tried but i couldn't :(

I tried but i couldn't

Then, I guess you are hosed.

zhirantaha: I tried but i couldn't :(

Try harder. If there are uses that you can't see how to remove then you can always ask here.