One of the many features of Safari is the ability to use the pinch to zoom feature on track pads and the magic mice. This is useful for zooming in on image and webpages. If, however, you don’t seem to have this ability all of a sudden with the latest version of Safari or Mavericks there is a solution to this problem. It turns out after a lot of digging and searching the implementation of Adblock causes this ability to be disabled. However by restarting the extensions within Safari this problem is solved.
To enable pinch to zoom within Safari open up the extensions preferences pane. This is located from the menu bar under Safari > Preferences > Extensions. Slide the extensions slider in the top right of the pane to the off position.
Close down Safari and re-open it. You should now notice that the pinch to zoom feature in Safari now works.
You can can go back into the extensions preference pane to re-enable the extensions.
It is a simple tip, however for those who have magically found that pinch to zoom no longer works it is a simple solution.