NOTE: This project contains resource errors, so aapt did not succeed, which can cause rendering failures. Fix resource problems first.

NOTE: This project contains resource errors, so aapt did not succeed, 
which can cause rendering failures. Fix resource problems first.

Failed to convert @drawable/nav_bar into a drawable
Failed to convert @drawable/hr_line into a drawable
Couldn't resolve resource @drawable/nav_bar
Couldn't resolve resource @drawable/hr_line
Exception details are logged in Window → Show View → Error Log

If you get such errors in Eclipse Android SDK's Graphical Layout then the reason may be some missing XML or images under res-> drawable folder, if you read carefully below the note error message you would see that reasons causing these errors, for me its because I have used nav_bar.xml, hr_line.xml resources in my current layout but are missing under drawable folder.

Simply add the missing files are stated in the note.