[nfbcs] Javascript code review for a calculater that isn't complete but had errors with validation

Tue Nov 22 23:30:12 UTC 2016

<!DOCTYPE html
 PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
        "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
      <html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en">
        <head>

          <title>Accessible calculater</title>
        </head>

        <body>
          <!-- ... body of document ... -->
        </body>
label for"first number">Enter the first number</label>
<input type="text" title="Enter first number:" label="first number"
alt="first number" name="first number" />
<label for"operation">Choose operation</label>
<input type="text" title="opperation"  name="opperation"/>
<label for"2nd number">Enter the second number</label>
<input type="text" title="2nd number"/>
<input type="button" title="calculate" name="calculate"
onclick="Display result"/>
</form>
<script>
<function_add numbers()
{
var first_number=int.parse(Document.GetElementById("Text1").value;
var second_number=int.parse(Document.GetElementByID("Text2").value;
var result="first_number+second_number");
document.getElement"txtresult").value=result;
</script>
</body>
</html>
I am having these issues:
WarningNo Character Encoding Found! Falling back to UTF-8.
None of the standards sources gave any information on the character
encoding labeling for this
'

I also don't know where to go from here, as i am a starter in javascript