Even with frequent cleanings Facebook is getting slower and harder.
Additional System Details
- User Agent: Mozilla/5.0 (Windows NT 6.0; rv:37.0) Gecko/20100101 Firefox/37.0
Is this problem on your Windows Vista system (somehow your post ended up in the FirefoxOS Phone category)?
The typical FB page contains content from many, many sources, and if any one of them is slow, that can create issues. If you watch the lower left corner of the page for status messages (such as reading, waiting, etc.), do you notice any particular servers causing problem? Sometimes using add-ons that block ads or scripts or disable unnecessary Flash content can help streamline sites.
When Firefox crashes, it usually records information about what was happening at that moment. You often will see the Mozilla Crash Reporter dialog come up. You can submit that data to Mozilla and share it with forum volunteers to see whether it points to the solution. Please check the last section of the support article "Firefox crashes - Troubleshoot, prevent and get help fixing crashes" for steps to get those crash IDs, and then post some of the recent ones here.
P.S. Cookies usually are very short, the length of words or a sentence. It probably won't speed things up to block cookies.