I used to wonder this warning when I started Android programming. You can safely ignore it as Android environment and compilation doesn’t require nor need it. Fortunately, there is a way to make it disappear. It might take awhile like a minute for the yellow warning mark to disappear after going through the instructions. Restart Eclipse if you’re hasty minded.
- Window -> Preferences
- Expand XML
- Expand XML Files
- Select Validation
- Choose “Ignore” from the “Indicate when no grammar is specified” combo
- Build -> Clean…
- Right click project -> Build Project
You might also want to check the original source for my tip. Note that restarting is not required.