follow these steps:
1. Type about:config in the address bar and hit enter.
2. Click on "I’ll be careful, I promise!". Don’t just say that and do wrong! You should be careful.
3. Now in the "Filter" box, type the ones given below one by one along with changing the value of each one to true.
NOTE: To change the value, just double-click on the required one.
network.http.pipelining
network.http.proxy.pipelining
network.dns.disableIPv6
plugin.expose_full_path
javascript.options.jit.chrome
javascript.options.jit.content
4. Now type network "http.pipelining.maxrequests" in the filter box and change its value to the number of tabs you open in Firefox at a time. For example, if you usually open 10 tabs, then put its value to 10. Just double-click on it to change the value.
5. Now right-click anywhere on the about:config page and select select "Integer" from the "New" option. Type content.notify.backoffcount and click on OK. Now set it its value to 5.
NOTE: Mac users could use Ctrl + click instead of right-click.
6. Again right-click anywhere on the page and select "Boolean" from New. Type "content.notify.ontimer" in the box and set its value to "true".
7. Right-click and select "Integer" from "New" and enter content.notify."interval" as the preference name and give its value to 500000. It speeds up web page loading.
8. Select another "Integer" and give the name as "content.switch.threshold" and set the value to 250000. This is also done to speed up the loading time of web pages.
9. Create another Boolean named "content.interrupt.parsing" and set its value to true.
10. Select "Integer" from "New once" again and give the preference name as "content.max.tokenizing.time" and set its value to 2250000.
or
>>Using add-ons like:
-Fasterfox could speed up your Firefox browser https://addons.mozilla.org/en-US/firefox/addon/9148/
- FastFox https://addons.mozilla.org/en-US/firefox/addon/9825/
-FireDownload https://addons.mozilla.org/en-US/firefox/addon/10615/
-Vaccum Places https://addons.mozilla.org/en-US/firefox/addon/13824/
-Speed DNS ( Make browsing faster ), https://addons.mozilla.org/en-US/firefox/addon/54648/
-Tweak Network ( Speed up web page loading ) https://addons.mozilla.org/en-US/firefox/addon/327/
>>You could also block the advertisements in web pages using Adblock Plus add-on to speed up web page loading https://addons.mozilla.org/en-US/firefox/addon/1865/
^_^