Ethernet PHP control - I want to stay in a loop and check for a new string

Just trying this out at the moment, does not work though. The LED starts flashing but again after that the arduino does not respond?

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

boolean flashing = false;

byte mac[] = { 
  0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED }; //physical mac address
byte ip[] = { 
  192, 168, 0, 177 }; // ip in lan
byte gateway[] = { 
  192, 168, 1, 1 }; // internet access via router
byte subnet[] = { 
  255, 255, 255, 0 }; //subnet mask
EthernetServer server(80); //server port

String readString;


void checkFor(){
  // 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);
        }

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

          /////////////// 
          client.println("HTTP/1.1 200 OK"); //send new page
          client.println("Content-Type: text/html");
          client.println(); 
          client.println("<HTML>");
          client.println("<HEAD>");
          client.println("<meta name='apple-mobile-web-app-capable' content='yes' />");
          client.println("<meta name='apple-mobile-web-app-status-bar-style' content='black-translucent' />");
          client.println("<link rel='stylesheet' type='text/css' href='http://homeautocss.net84.net/a.css' />");
          client.println("<TITLE>Home Automation</TITLE>");
          client.println("</HEAD>");
          client.println("<BODY>");
          client.println("<H1>Home Automation</H1>");
          client.println("<hr />");
          client.println("
");  
          client.println("<a href=\"/?flashing\"\">Flashing</a>");      
          client.println("<a href=\"/?lighton\"\">Turn On Light</a>");

          client.println("<a href=\"/?lightoff\"\">Turn Off Light</a>
");         
          client.println("</BODY>");
          client.println("</HTML>");

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

          ///////////////////// control arduino pin
          if(readString.indexOf("?lighton") >0)//checks for on
          {
            digitalWrite(7, HIGH);    // set pin 4 high
          }
          else if(readString.indexOf("?lightoff") >0)//checks for off
          {
            digitalWrite(7, LOW);    // set pin 4 low
          }
          else if(readString.indexOf("?flashing") >0)
          {
            flashing = true;
          }


          //clearing string for next read
          readString="";
        }
      }
    }
  }


}


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

void setup(){

  pinMode(7, OUTPUT); //pin selected to control
  //start Ethernet
  Ethernet.begin(mac, ip, gateway, subnet);
  server.begin();

}

void loop(){

  if (flashing == true) 
  {
    digitalWrite(7, LOW);
    delay(100);
    digitalWrite(7, HIGH);
    delay(100);
    checkFor();
  }
  checkFor();

}