Make your Firefox Faster

This is actually the old trick, but still works well.

It's work for me, so I hope the same for you

Pipelining requests
It allows for more simultaneous connections to web servers. Note that the HTTP specs suggest for 4 concurrent connections. Setting this value to 10 allows for more web page components being downloaded at the same time, noticeably improving browsing. To appy the tweak, follow the simple instructions below:
1. In the address bar, type:  about:config
2. Locate and change the following values (by double-clicking on them):
   Make sure --> network.http.version is set to 1.1
   network.http.keep-alive = true
   network.http.max-connections = 48 (default is 24)
   network.http.max-connections-per-server = 10 (default is 8)
   network.http.max-persistent-connections-per-proxy = 16 (default is 4)
   network.http.max-persistent-connections-per-server = 8 (default is 2)
   network.http.pipelining = true (default is false)
   network.http.pipelining.maxrequests = 10 ( default is 4)
   network.http.proxy.pipelining  = true (default is false)

3. Optionally, you can also tweak the following settings:
   content.notify.backoffcount = 5
   ui.submenuDelay = 0
   network.http.pipelining.maxrequests = 30 (for BROADBAND user)

Note: Setting the number of connections per server to a much higher number (over ~10) can cause web servers to drop some requests, resulting in incomplete pages, increased retransmissions, etc., so it is not recommended.


Reduce Initial Page Delay
By default, Firefox waits 0.25 seconds (250ms) before beginning to draw web pages. To reduce this initial delay, do the following:
1. In the browser address bar, type: about:config
2. Anywhere in the browser window, right-click and create: NEW > String
3. Name the string:  nglayout.initialpaint.delay (no spaces) and set its value to an integer between 0 and 50 (something sensible, in milliseconds).

Note: This setting is not present by default. When not present, Firefox waits 250 milliseconds before first displaying the page.


Advanced Firefox Settings
Below, you will find settings that may increase your perceived page loading time a bit further. Note that those are most likely best left at the default values. These settings generally do no exist under the Firefox about:config, and need to be created if you'd like to experiment with them.
bolean for --> true or false
integer for --> numbers

content.interrupt.parsing - default/recommended is true. When true, parsing can be interrupted to process User Interface events.
When false Firefox will ignore UI events altogether until the current page has been downloaded. This is a little drastic as Firefox could remain unresponsive for quite some time, but try this and see how it works for you.
content.max.tokenizing.time recommended value = 2250000. Defines maximum number of microseconds between reflows.
content.notify.interval - recommended value = 750000
content.switch.threshold – recommended value = 750000
content.notify.ontimer - recommended set to true. If so, doesn't reflow pages more often than the content.notify.interval timer.
browser.cache.memory.capacity - recommended value = 65536


Note:
content.switch.threshold - raising the value will make the browser more responsive at the expense of page load time.
browser.cache.memory.capacity - memory, in KB reserved for caching decoded images. Default varies with RAM.