The release of a DNS poisoning exploit into the wild this week means that you could potentially be redirected to a cloned website when surfing the net. Given the risks that suggests (especially if you do anything online shopping-wise) its probably a good idea to check your DNS server for its security.
The easiest way of doing this? Click here and take the test. If your DNS server comes back as being at risk then switch to OpenDNS by following the instructions here.
And even if your DNS server appears to be good you're probably as well to change anyway as you'll benefit from generally better security, more features and more speed than your ISP assigned DNS.