// проверено в IE
function moveCaretToStart(inputObject)
{
 if (inputObject.createTextRange)
 {
  var r = inputObject.createTextRange();
  r.collapse(true);
  r.select();
 }
}

function moveCaretToEnd(inputObject)
{
 if (inputObject.createTextRange)
 {
  var r = inputObject.createTextRange();
  r.collapse(false);
  r.select();
 }
}

// проверено в FireFox

function moveCaretToStart(inputObject)
{
 if (inputObject.selectionStart)
 {
  inputObject.setSelectionRange(0,0);
  inputObject.focus();
 }
}
function moveCaretToEnd(inputObject)
{
 if (inputObject.selectionStart)
 {
  var end = inputObject.value.length;
  inputObject.setSelectionRange(end,end);
  inputObject.focus();
 }
}