Form

Typical code that validate form on submit.

<script language="JavaScript">
myFunctionName() {
    if (document.myForm.myText.value == '')
        return false;
        // When it returns false - your form will not submit and will not redirect too
    else
        return true;
     // When it returns true - your form will submit and will redirect
// (actually it's a part of submit) id you have mentioned in action
}
</script>

<form name="myForm" onSubmit="return myFunctionName()">
<input type="text" name="myText">
<input type="submit" value="Click Me">
</form>