SDFAT.h , write files and web server

So i have made a cod wich makes some files and should make me able via web to see the fiiles and download them. But i have some problems. I understand that i need this line of code if (!sd.begin(10, SPI_HALF_SPEED)) sd.initErrorHalt(); to bee able to make files and folders (it was someting other than 10 but i dont remember know what it was, howeer its the same) but if i use this then i cand open files via webserver :S I can open the ip 192.168.10.108 and it shows files and folders in root, but i cant open them, if i try it says that files not exists. When i delete the !sd.begine line, i can open the files but cannot create any :S why is that so, and how to fix it please?

here is the setup funciton

void setup() {
  Serial.begin(9600);

  PgmPrint("Free RAM: ");
  Serial.println(FreeRam());  

  // initialize the SD card at SPI_HALF_SPEED to avoid bus errors with
  // breadboards.  use SPI_FULL_SPEED for better performance.
  pinMode(10, OUTPUT);                       // set the SS pin as an output (necessary!)
  digitalWrite(10, HIGH);                    // but turn off the W5100 chip!


  pinMode(I1,INPUT);
  pinMode(I2,INPUT);
  pinMode(I3,INPUT);
  pinMode(U1,INPUT);
  pinMode(U2,INPUT);
  pinMode(U3,INPUT);
  setTime(23, 59 , 23 ,31, 10, 2013);
  if (!sd.begin(10, SPI_HALF_SPEED)) sd.initErrorHalt();
  if (!card.init(SPI_HALF_SPEED, 4)) error("card.init failed!");

  // initialize a FAT volume
  if (!volume.init(&card)) error("vol.init failed!");



  PgmPrint("Volume is FAT");
  Serial.println(volume.fatType(),DEC);
  Serial.println();

  if (!root.openRoot(&volume)) error("openRoot failed");

  // list file in root with date and size
  PgmPrintln("Files found in root:");
  root.ls(LS_DATE | LS_SIZE);
  Serial.println();

  // Recursive list of all directories
  PgmPrintln("Files found in all dirs:");
  root.ls(LS_R);

  Serial.println();
  PgmPrintln("Done");

  // Debugging complete, we start the server!
  Ethernet.begin(mac, ip);
  server.begin();

It should be D4 for the SD slave select if this for an ethernet shield. D10 is the SS for the w5100, not the SD.

if (!sd.begin(4, SPI_HALF_SPEED)) sd.initErrorHalt();

ok it works now, the main problem was that i called the function which needed to control web-server client and give it access to the fules in a loop wich had an open file already, apperantly if an file is open then webserever cannot conect the client to the files, however solved this one. Now i need to know is there an fuction to see if the sd card is full, i want to programe it so that if the sd card is full it gives me an error output.