Understanding Prefetching

This post describes an interesting concept called “Link Prefetching in Web Pages”. It talks about the ways to design Prefetching within your webpages and also talks about the issues attached with it.

What is meant by Prefetching in Web parlance?

In order to understand Prefetching, we need to understand how a web page with multiple objects like images, stylesheets etc is loaded by a Browser. In a usual scenario, we always have a web page designated as the HTML rendered by the browser. This webpage then has the embedded objects like images ( jpeg,gif,png etc) , stylesheets ( css ) etc. When the user makes a request for such a webpage, the first thing a web browser does is load the HTML. The browser then parses the HTML and asks for the different objects in a top-down fashion.

Skeleton of a Web Page.

Skeleton of a Web Page.

The above figure explains the request flow for a hypothetical web page with HTML, Images, FLV, Javascript and CSS. The numbers written against the component refers to the way they would be requested by the browser.

So if you have a script written at the top of the web page, that will get loaded first, then whatever next. What is important to understand is that the next request from the browser is made only when the first request has completed. This ways, the browser waits for the first object request to complete before issuing the next request. This leads to a lot of wait time, which in turn can make your website appear to be slow.

With Prefetching, the web browser tries to resolve this issue. When Prefetching is enabled, the browser requests for the first object (i.e. the html) and while it delivers and renders the response to the end user, also parses the HTML to figure out the next subsequent requests. It then makes those requests Asynchronously and stores the result in its browser cache. Therefore, the wait time between the two results is reduced. When the user actually asks for that content, all the browser has to do is give that object from its Cache. The object appears immediately, thereby giving an impression to the end user that the website is indeed fast. Read more about How to get data from the browser cache in Firefox.

How to design my HTML to enable link Prefetching?

The browser looks for either an HTML link tag or an HTTP Link: header with a relation type of either next or prefetch. An example using the link tag follows:

<link rel="prefetch" href="/images/big.jpeg">

The same prefetching hint using an HTTP Link: header:

Link: </images/big.jpeg>; rel=prefetch

The Link: header can also be specified within the HTML document itself by using a HTML meta tag:

<meta http-equiv="Link" content="&lt;/images/big.jpeg&gt;; rel=prefetch">

Please note that even if you dont have these special tags in place, some browsers/ applications can still prefetch your links.

I am a Web Administrator, How can i identify Prefetch requests from the Browser client?

Yes. Firefox sends a special request header X-moz: prefetch for Prefetch requests. You can setup your server to track these requests seperately or block them totally, as the case may be.

If you are a web admin and seeing lot of traffic on your server, firstly identify Prefetching requests from your Server Access Logs and then in order to take control of the situation related with prefetching process, decide upon a rescue strategy.

Do i need any special kind of Browser for the Prefetching to work?

Almost all the web browser these days, support Prefetching. All you need to ensure is that your browser supports prefetching and it is enabled. Test if your browser supports Prefetching.

Are there any issues with Prefetching?

There are no serious issues attached with Prefetching but yes, you may find your bandwidth being utilized for content which you might never actually view. 

The other issue is related to prefetching of certain links with topics which might be illegal in your geography.

Your Web site statistics data may become less reliable because of statistics registered for page hits that were never seen by the user

Can i disable Prefetching in Firefox? How do i disable Prefetching in Firefox?

Yes. Though, by default Prefetching is turned on in Firefox, but it can be disabled by following the steps mentioned below.

1.) Open the Firefox browser

2.) Type about:config in the address bar and press Enter

3.) Scroll down the resulting preference list to network.prefetch-next

Disabling Prefetching in Firefox

Disabling Prefetching in Firefox

4.) Double click network.prefetch-next so the value is set to false.

5.) Close Firefox and restart it to enable the change.

Can you list any other Softwares or Add-ons which use Prefetching technique to help me gain some time?

Well, there are many but the two most famous one’s are Google Web Accelerator and an interesting Firefox Add-On for speeding up Firefox called FasterFox.

References: Mozilla

Also Read: Firefox 3.1 to add Private Browsing feature

[How-To] Open Firefox Bookmarks Using Keywords

Mozilla Firefox: Get the data from your Cache

Do you store your passwords using Firefox?

You can follow me on Twitter at http://twitter.com/vaibhav1981

Do stay tuned to Technofriends for more, one of the best ways of doing so is by subscribing to our feeds. You can subscribe to Technofriends feed by clicking here.

Cheers

Vaibhav Pandey

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Interesting Free RSS Icons For Your Feed Subscription Links

Speckyboy has an interesting post on 22 Free RSS Styles for your blog. You can choose anyone of those free RSS Icons to give more Jazz to your blog. Check out some of the featured icons below. 

Free RSS Icons for your Blog.

Free RSS Icons for your Blog.

In order to check all the icons, Check out the entire post on Speckyboy.

Also read: [How-To]Transform any RSS feed into an iPhone friendly site.

Google Reader now translates feeds to your language on the fly

Firefox Addon UrlbarExt extends your Location bar

 

You can follow me on Twitter at http://twitter.com/vaibhav1981

Do stay tuned to Technofriends for more, one of the best ways of doing so is by subscribing to our feeds. You can subscribe to Technofriends feed by clicking here.

Cheers

Vaibhav Pandey

The Ultimate Student Resource List

Check out this ultimate and exhaustive list of free software and useful websites. Though, the title sounds more for students but believe me the list is relevant for everyone and not just limited to students.

Student Resources

Student Resources

Some of the very interesting softwares covered are FreeMind; free mindmapping software, Zotero; A bibliography manager that integrates with Firefox, allowing you to automatically add webpages and, more usefully, resources from academic databases like J-Stor and AnthroSource to your bibliography. 

Interestingly, the list also covers some very useful internet research resources like encyclopedias and online study guides. Worth a look, especially for those who are looking out for Student resources.

Some additions to the list maybe

1.)  del.icio.us: del.icio.us is a great service for bookmarking interesting articles and other useful links on your university’s webpage. Tag lots to make searching for bookmarked links or articles easier,later. Its better than bookmarking stuff on your browser. You can also check out other reader’s bookmarks.


2.) Invest in a good flash and load it up with portable apps like
OpenOffice, Firefox, and Pidgin amongst others. 


3.) Calendar. Having a good calendar (as well as a to do list) is a big booster in staying organized and keeping on top of assignments. Try using
Google Calendar

Do check this complete list at Lifehack.

Also read: [How-To] View Webcontent without Passwords

[How-To] Remove USB Devices Safely

[How-To] Learn languages using iTunes

[How-To] Recover lost Outlook PST Password

 

You can follow me on Twitter at http://twitter.com/vaibhav1981

Do stay tuned to Technofriends for more, one of the best ways of doing so is by subscribing to our feeds. You can subscribe to Technofriends feed by clicking here.

Cheers

Vaibhav Pandey

Will you use Google App Engine with Java Support?

On a poll being run on Technofriends earlier, 70% voters said they will use Google App engine once it has Java support enabled. 

Do you use Google App Engine

Poll Results: Do you use Google App Engine

Out of 251 total votes casted, 178 votes were polled for the option which said ” I plan to use it when Java Support is Enabled.” 

Seems like we have interesting times coming with Java support for Google App Engine already announced.

Thanks to all the readers who took some time out for casting their valuable votes. The poll is still open and if you wish to cast your votes, please do so by selecting one of the options ( see below).

You can follow me on Twitter at http://twitter.com/vaibhav1981

Do stay tuned to Technofriends for more, one of the best ways of doing so is by subscribing to our feeds. You can subscribe to Technofriends feed by clicking here.

Cheers

Vaibhav Pandey


EvaPhone: Make free International calls

If you wish to make a short International call and that too for free, EvaPhone is the website to check.

EvaPhone provides Internet telephone calls for free using VoIP service which lets you make PC-to-phone free international calls. All you need is a computer to start making free VoIP calls using Internet to phone.

Use Evaphone to make a Free International call.

Use Evaphone to make a Free International call.

While you make your short call, Evaphone shows a you a small advertisement.

Start enjoying the benefits of Internet telephony right now!

Also read: [How-To] Make a free call to your buddies using Fring.

Send Free SMS in India using 160by2

Skype announces Unlimited International calls.

Multiple Ways to Access Twitter from your Mobile Phone.

You can follow me on Twitter at http://twitter.com/vaibhav1981

Do stay tuned to Technofriends for more, one of the best ways of doing so is by subscribing to our feeds. You can subscribe to Technofriends feed by clicking here.

Cheers

Vaibhav Pandey

Go! Animate: Create animations with Ease

If you are one of those who doesnt possess a good technical knowledge of Softwares like Flash or is someone who struggles with his/her drawing talent, Go! Animate is the website to check.

Go! Animate Logo

Go! Animate Logo

The site provides users with a library of interesting characters, backgrounds, props, sound effects and music for use in creating their own unique animations. Creators can customize their animations with a number of tools and features that allow them to create truly unique works of expression.

Animations from Go! Animate

Animations from Go! Animate

The website gives you an opportunity to Create your own animations, or Watch animations created by others.

Check out Go! Animate and do let me know if you know of any similar sites.

Also read: Some Websites To Help You Stay Healthy and Fit

Get Free Images for your Blogs

Create Professional Business Logos for Free

My-Image-Size: Online Image Resizer

You can follow me on Twitter at http://twitter.com/vaibhav1981

Do stay tuned to Technofriends for more, one of the best ways of doing so is by subscribing to our feeds. You can subscribe to Technofriends feed by clicking here.

Cheers

Vaibhav Pandey

[How-To]Transform any RSS feed into an iPhone friendly site.

If you own a blog or any rss feed which you wish to create a neat site out of it for your iPhone subscribers, DoYouFeed is the website to check. By the way this can as well be a good strategy for reader delight and also create a buzz about your blog.

doYouFeed logo

doYouFeed logo

In order to enable your feed or blog as an iPhone friendly site, follow the steps below

1.) Point your browser to http://www.doyoufeed.com/us/index.php

DoYouFeed Add site

DoYouFeed Add your site

2.) In the textbox titled Add feeds and sites, enter your feed or site URL and press Add.

3.) Once done, DoYouFeed will give you options to tune your settings further, though, all the basic settings look good.

Technofriends on iPhone

Technofriends on iPhone

4.) Scroll down to see your iPhone friendly site URL.

If you wish to access Technofriends from your iPhone, click here or bookmark http://tinyurl.com/64jtkv

Doyoufeed offers the following features

Your iPhone friendly site built from ground for you has a lit of useful features (and many more to come) :

  • Fast load and lightweight pages
  • iPhone optimized navigation
  • Mix several feeds in one unique site
  • Different themes available
  • Automatic page refresh
  • Relative date (2 hours ago, yesterday, monday…)
  • Preview of news content on the news list
  • Share news via email and social sites
  • Nothing to install on your iPhone
  • No registering required

Via: Makeuseof.com

Also read: Watch Online TV Channels: Live & Free

Recovering ‘permanently’ deleted email in Microsoft Outlook 2003

[How-To] Missed Outlook Attachment,get warned before its too late

Bose’s iPod Docking Station: A clear winner

 

You can follow me on Twitter at http://twitter.com/vaibhav1981

Do stay tuned to Technofriends for more, one of the best ways of doing so is by subscribing to our feeds. You can subscribe to Technofriends feed by clicking here.

Cheers

Vaibhav Pandey