Wireless Rickroll using Arduino
No particular comment on the Arduino-specific or Wifi-specific stuff, but here:

currentssidno = currentssidno + 1;
if (currentssidno == 6) //please change this count if you change the amount of ssids
{
  currentssidno = 0;
}


Two things. First, you can rephrase this conditional logic as simply

currentssidno += 1;
currentssidno %= 6;  // please change this, etc.


or equivalently

currentssidno = (currentssidno + 1) % 6;  // please change this, etc.


depending on where you'd prefer to repeat the name currentssidno. (I'd probably rename that variable to i and then use the latter form.)

Secondly, don't hard-code magic numbers like 6, if you can express them as "non-magic" numbers such as "the size of this particular array I've got".

// Put this macro in your toolkit. You'll use it frequently.
#define DIM(arr) (sizeof (arr) / sizeof (arr)[0])

/* ... */
currentssidno = (currentssidno + 1) % DIM(ssids);


Now you no longer need the comment, because the code no longer has that weird subtle dependency on the length of the ssids array. It Just Works, no matter what ssids you want to use.