cvc-elt.1: Cannot find the declaration of element 'LinearLayout'

[deltalein]

I am using xml to define my UI for an Android app using Netbeans (7.1). My main.xml looks like this...\[code\]<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:id="@+id/Layout01" androidrientation="vertical" android:layout_width="fill_parent" android:layout_height="fill_parent" androidaddingLeft="10dp" androidaddingRight="10dp" > <EditText android:layout_width="fill_parent" android:layout_height="wrap_content" android:hint="@string/to (phone #)" /> <EditText android:layout_width="fill_parent" android:layout_height="wrap_content" android:hint="@string/date" /> <EditText android:layout_width="fill_parent" android:layout_height="wrap_content" android:hint="@string/subject" /> <EditText android:layout_width="fill_parent" android:layout_height="0dp" android:layout_weight="1" android:gravity="top" android:hint="@string/event description" /> <Button android:layout_width="100dp" android:layout_height="wrap_content" android:layout_gravity="right" android:text="@string/send" /> </LinearLayout>\[/code\]When I attempt to validate my the xml (file) I receive "cvc-elt.1: Cannot find the declaration of element 'LinearLayout'". Also, my Java class (MainActivity) now shows an error indicating that it can't find the R.Layout.main class. I've searched the internet far and wide with no luck. Can someone please help? Thanks,