Go step by step and test.
1. Startup in Safe Mode and restart normally by clicking the “Restart” button at the bottom.
Start up in Safe Mode.
http://support.apple.com/kb/PH11212?viewlocale=en_US
2. Safari > Preference > Advanced
Checkmark the box beside "Show Develop menu in menu bar".
Develop menu will appear in the Safari menu bar.
Click “Develop” to show the dropdown.
Click "Empty Caches" from the dropdown and test.
3. Disable Extensions and test.
Safari > Preferences > Extensions
Select and disable all extensions and test.
Enable Extensions one by one and test.
To uninstall any extension, select it and click the “Uninstall” button.
4. Delete com.apple.Safari.plist file and test.
Backup your Mac.
Empty the Trash.
Quit all applications.
Hold the option key down and click the "Go" menu in the Finder menu bar.
Select "Library" from the drop down. Click "List" view in the Finder toolbar
Library > Preferences > com.apple.Safari.plist
Right click on it and select "Move it to Trash".
Restart and relaunch Safari. Click “Start using Safari” link at the bottom.
If this doesn’t help, “Put Back” the com.apple.Safari.plist
Right click on the Trash icon in the Dock and select “Open”.
Right click on the com.apple.Safari.plist and select “Put Back”.
Choose”Replace”.