When you only have a smaller dog, climbing or jumping over a tall fence may not be much of a problem, however, digging underneath it might be. Larger dogs are the one that are most likely to be able to find a way to climb over a fence. Chain link fences are especially easy for big dogs to climb over because of the holes. The holes in chain link are perfect to get their paws into and use as a ladder to climb over.
The reason dog owners fence their yards in the first place is to keep the dog in your yard and out of neighboring yards. Of course, fences are also put up to keep your dog safe from other dogs or from traffic on the road. For some dogs, a fence is just a challenge to them. They want out and they will try whatever they can to get out!
If you have a serious problem with your dog climbing a fence or even digging underneath it, I went to http://www.doggybakery.org/stop-dog-jumping-fence/ and found the perfect solution for my dog. There are a number of options available to prevent fence climbing. Coyote rollers are one such solution. Electric wire at the top is another solution and invisible fencing has become a very popular option. Check each of these solutions before you make a final decision. They all vary in price and ease of installation.