How can I diagnose the problem behind the delay I get when changing tabs in Firefox? It is up to about 1.5 seconds.

To provide some background, I use three monitors and often have three Firefox windows open at the same time. My machine should be fast enough, it is a `AMD Phenom II X6 1055T` at 2.8GHz, a `NVIDIA GeForce GTX 660` and 4GB of RAM.

The issue appears to be stronger for some webpages. For example, the Wordpress backend, the FireFTP addon tab, Google Mail, are slower than simple pages like Google Search, or static HTML pages.