I bought a new Macbook Air a month ago. It's perfect, but when I use Safari, sometimes I expreienced a problem like that picture.
What's wrong with my Macbook?
MacBook Air (13-inch Mid 2013), OS X Mountain Lion (10.8.4)
Installed any third party fongs since purchasing your Mac?
If so, launch Font Book located in the Applications Folder.
From the Font Book menu bar click File > Restore Standard Fonts
Restart your Mac and try Safari.
If fonts aren't the issue, try emptying the Safari cache.
Press Command + Option + E then quit and relaunch Safari to test.
If that doesn't help, try troubleshooting extensions and third party plug-ins.
From your Safari menu bar click Safari > Preferences then select the Extensions tab. Turn that off if there are any installed. Quit and relaunch Safari to test. If that helped, turn extensions back on then uninstall one a time to test.
If it's not an extensions issue, try troubleshooting third party plug-ins.
Back to Safari > Preferences. This time select the Security tab. Deselect: Allow all other plug-ins. Quit and relaunch Safari to test.
If that made a difference, instructions for troubleshooting plugins here.
Macbook Air 2013(Mid) Display Problem
