How to change size of readstring() in client.read() on Arduino Ethernet?

Try this one and check the sram:

/* 
 Web server sketch for IDE v1.0.1 and w5100/w5200
 Posted October 2012 by SurferTim
 */

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

byte mac[] = { 
  0x00, 0x00, 0xAA, 0xBB, 0xCC, 0xDD }; //physical mac address
byte ip[] = { 
  192, 168, 10, 110 }; // ip in lan
byte gateway[] = { 
  192, 168, 10, 254 }; // internet access via router
byte subnet[] = { 
  255, 255, 255, 0 }; //subnet mask
EthernetServer server(8070);

char user[ ] = "admin"; // YOUR Username for Login
char pwd[ ] = "123abc"; // YOUR Password for Login
int loggedin = 0;
//////////////////////

void setup()
{
  Serial.begin(9600);

  // disable w5100 while setting up SD
  // uncomment next 5 lines if using a microSD card

  //  pinMode(10,OUTPUT);
  //  digitalWrite(10,HIGH);
  // Serial.print("Starting SD..");
  // if(!SD.begin(4)) Serial.println("failed");
  // else Serial.println("ok");

  Ethernet.begin(mac, ip, gateway, gateway, subnet);

  delay(2000);
  server.begin();
  Serial.println("Ready");
}

void loop()
{

  Serial.println("11");   
  EthernetClient client = server.available();
  if(client) {
    Serial.println("12");   
    boolean currentLineIsBlank = true;
    boolean currentLineIsGet = true;
    int tCount = 0;
    char tBuf[64];
    
    Serial.print("Client request: ");

    while (client.connected()) {
      Serial.println("13");   
      while(client.available()) {
        Serial.println("14");   
        char c = client.read();

        if(currentLineIsGet && tCount < 63)
        {

          tBuf[tCount] = c;
          tCount++;
          tBuf[tCount] = 0;          
        }


        if (c == '\n' && currentLineIsBlank) {
          // send a standard http response
          Serial.println(tBuf);
          Serial.print("POST data: ");
          while(client.available()) Serial.write(client.read());
          Serial.println();



          Serial.println("Sending response");
          client.write("HTTP/1.0 200 OK\r\nContent-Type: text/html\r\n\r\n<html>");

          client.write("<head><script type=\"text/javascript\">");
          client.write("function show_alert() {alert(\"This is an alert\");}");
          client.write("</script>");
          client.write("<TITLE>NaThAN Home Server Login Page</TITLE>");
          client.write("  </head");


          client.write("<body>");

          client.println("<CENTER>");
          client.println("<img src=\"https://dl.dropbox.com/u/28103209/HomeServer_files/login_nathan_homeserver.gif\"  width=\"460\" height=\"36\" >");
          client.println("</CENTER>");

          client.println("<CENTER>");

          client.println("<text STYLE=\"position:relative; TOP:50px; LEFT:50px;  WIDTH:50px; HEIGHT:50px\">");
          client.println("<FORM ACTION=\"http://nathanas.dyndns.info:8070\" method=get >");  //SET THE DOMAIN
          client.println("Username: <INPUT TYPE=TEXT NAME=\"username\" VALUE=\"\" SIZE=\"25\" MAXLENGTH=\"50\">
");
          client.println("Password: <INPUT TYPE=TEXT NAME=\"password\" VALUE=\"\" SIZE=\"25\" MAXLENGTH=\"50\">
");
          client.println("<text STYLE=\"position:relative; RIGHT:33px; TOP:10px; \">  ");
          client.println("<INPUT TYPE=SUBMIT NAME=\"submit\" VALUE=\"Log In\">");
          client.println("</FORM>");
          client.println("</CENTER>");



          client.write("</body></html>\r\n\r\n");
          client.stop();
        }
        else if (c == '\n') {
          currentLineIsBlank = true;
          currentLineIsGet = false;
        } 
        else if (c != '\r') {
          currentLineIsBlank = false;
        }
      }
    }

    Serial.println("done");


   



    if(strstr(tBuf,user) != NULL  && strstr(tBuf,pwd) != NULL )//Successful login
    {
      loggedin=1;
      digitalWrite(9, HIGH);    // set pin 4 high
      Serial.println("Login Successful!");         
    }






  }



}

Then try removing this from the above and then check the sram again...isn't that odd?

if(strstr(tBuf,user) != NULL  && strstr(tBuf,pwd) != NULL )//Successful login
    {
      loggedin=1;
      digitalWrite(9, HIGH);    // set pin 4 high
      Serial.println("Login Successful!");         
    }