Many web services today offer tracking codes so that you can monitor interaction between your site and the service. Facebook, Twitter, and Instagram are examples of these services.
A potential problem with these tracking codes is that they can appear to slow down your site before the end user needs to load things from those services. If those services are slow then your site will appear slow.
A key to making included scripts like that behave properly is loading them properly and giving proper timeouts. Tracking Code Manager is an excellent plugin that does exactly that for a wide variety of services, and we recommend using it for all tracking codes.