I'm running v10.9 Mavericks and Safari 7 wtihout any issues using with searching using Command + F
From your Safari menu bar click Safari > Preferences then select the Advanced tab.
Select: Show Develop menu in menu bar
Now click Develop from the menu bar. From the drop down menu click Empty Caches.
Quit and relaunch Safari then try a search with Command + F
Maybe an incompatible extension ..
From the Safari menu bar click Safari > Preferences then select the Extensions tab.
Turn that OFF, quit and relaunch Safari to test.
If that helped, turn one extension on then quit and relaunch Safari to test until you find the incompatible extension then click uninstall.
I did what you proposed. And for good measure, I also emptied the caches prior to quitting and relaunching Safari. But no success. For the test, I tried Find on both a Wikipedia webpage and a New York Times webpage. No success on either.
Any reason to suppose that trashing the plist might help? Or doing a Safe Restart, just to see if it makes a difference?
Oddly, I just booted up Firefox, open the same webpages, and tried the Find function in Firefox, and it does not function either -- neither with the keyboard command, nor with Find from the menubar. Other Command-key functions work properly (e.g., Copy / paste).
This seems very strange.
My other desktop Mac, identical except that I have not upgraded to Maverick / Safari 7.0, works just fine on all this.
I had this problem too and I just found the solution here:
If you have once installed Glims you just have to remove it (It doesn't show with onther extensios in Safari's preference)
I followed your suggestion and did a Safe Boot, then tested Safari's Find function, and it worked as it should. Then I restarted my Mac, and sure enough, Safari's Finmd function once again would not work. Figuring I had nothing to lose by it, I followed the suggestion of others and did the Uninstall of Glims. I had not recollection of ever installing Glims, but what the heck.
And that did the trick. As soon as the Glims uninstall was done, and I restarted Safari, the Find function returned.
Problem solved. My ample thanks to you and others who pointed me toward the solution.