Dear Rioch,
As you still get a clear picture of those spaces, it looks as if only the touchscreen glass is concerned.
Do a hard-reset of your phone (holding Power and Home buttons simultaneously until you see the silver apple on black background appear), just to confirm that you are not looking at a software glitch.
Then head over to the Parts section of iFixit to get either a Front Panel (35$) or a Front Panel Assembly (70$) depending on you fixing skills.
See here:
iPhone 3G Front Panel
iPhone 3G Front Panel Assembly
Kind Regards,
Ronny
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