Sunday, March 30, 2008

Iframe ad-tag vs. Script ad-tag: Online advertising tag type comparison

This is a list that I have discussed many times with friends, however I never found these on a single place so here you go ...

Differences between iframe tag and script tag:
  1. Iframe tag does not delay the loading of the web-page elements: Iframes usually load in parallel, so for example if you have several elements in a page like images, CSS, JavaScripts and HTML tags and you have the ad-tag as an iframe embedded in the page, the iframe loading would happen in parallel and it would not make your page loading slower. So, if you want page to load faster use iframe tags.
  2. Script tag does not change the “referrer” property of your ad-tag: If your ad-tag is served from inside an iframe, the ad-network that serves the ad will see a referrer property different that your page url/domain. On the other hand if you use a script tag, then the referrer url remains the same as your page url and therefore your domain name. Some ad-networks that require that the ad being served from the same domain that they were created for, will therefore not work with iframe tags (therefore they will not serve ads). Most ad-networks however allow setting of a “site-alias” that allows you to set a different domain from which the ad may be served. Read more about the referrer property here.
  3. Script tag works better for ad-networks that do contextual analysis of the content of the page: if you use iframe tags, ad-networks will not be able to look outside of the iframe therefore they will not be able to do on-the-fly contextual analysis of the contents of the page, therefore they may serve irrelevant ads. Read more about contextual analysis here.
  4. If there is more than one ad from the same ad-network, and you are using iframe tags, these ads may not be able to communicate amongst themselves since the scope of the JavaScript variables is within an iframe. Therefore if an ad-tag sets a JavaScript variable, which the other ad-tag on the same page is expected to read, this will break if you use iframe tags.
  5. Since JavaScript variables have their scope only within that iframe, they don’t contaminate the namespace of the JavaScript variables of your web-page, neither do they get affected by the JavaScript variables of your web-page.
  6. Iframe tags are easier for inclusion inside a web-page, since you can save an ad-tag in a file, and load it as an iframe into your web page. This will also allow parallel load of the ad-tag iframe. For example if your web-page is:

<script type=”” …>


More questions? Drop me an email.

Update: For #3 "Script tag works better for ad-networks that do contextual analysis", Google AdSense does mention in their help section for Why aren't my ads relevant?, read on:
The AdSense code was placed within an IFRAME.
Our targeting technology is not optimized to serve ads within a separate IFRAME. If you placed the AdSense code in a separate IFRAME, your site may display less targeted ads or public service ads. For better results, please implement our ad code directly into the source of your webpage. Once you make these changes, relevant ads may not appear immediately. Until we are able to re-crawl your site, which may take up to 48 hours or more, your page may continue to display untargeted or public service ads.

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Thursday, March 20, 2008

Disk storage - where are we headed?

Some insightful articles and some of my own thoughts on the trends in data storage:

Disk capacities are going up and costs are going down, however the effective transfer bandwidth (ETB) per byte of capacity has come down tremendously. Despite capacities and transfer rates increasing by factors or 10,000 and 100 respectively, typical drive ETB has actually decreased by a factor of 100. As Jim Gray said "Disks have become tapes." (Link to source).

Consider, for example, a 10 TB database. Ten years ago, this database would have occupied two thousand 5 GB drives - a common size at the time. With a 3 MB/second transfer rate, the aggregate bandwidth of these 2,000 drives would have been 6 GB/second, enabling the entire database to be scanned in about 30 minutes. Today, only about 20 higher-capacity drives would be needed to hold this same database. Those 20 drives would have an aggregate bandwidth of 1.2 GB/second, increasing the time required to scan the entire database to 150 minutes - an increase of two hours.

Jim Gray points out - We have to convert from random disk access to sequential access patterns. Disks will give you 200 accesses per second, so if you read a few kilobytes in each access, you're in the megabyte-per-second realm, and it will take a year to read a 20-terabyte disk. If you go to sequential access of larger chunks of the disk, you will get 500 times more bandwidth—you can read or write the disk in a day. So programmers have to start thinking of the disk as a sequential device rather than a random access device.

Tom White later says that - "MapReduce is a programming model for processing vast amounts of data. One of the reasons that it works so well is because it exploits a sweet spot of modern disk drive technology trends. In essence MapReduce works by repeatedly sorting and merging data that is streamed to and from disk at the transfer rate of the disk. Contrast this to accessing data from a relational database that operates at the seek rate of the disk (seeking is the process of moving the disk's head to a particular place on the disk to read or write data). Read more here.

My take is that SSDs are going to take a while to become an economically viable alternative to disks. Flash disks cost approximately $10/GB, and the OEM costs of good flash drives cost about $60/GB or more (source here). Compare this with the cost of disk, which is about $0.20/GB. So, we are looking at about 300x price difference here. So, I think, it's going to take while before SSDs become reality in storing terabytes of data. Until that time, we will have to use 50-70% empty disks to enhance striping-performance. So, if we were to use 50% empty disks, the cost of disks doubles for storing the same amount of data.

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MySQL - Is there a theoretical limit?

Guy Kawasaki interviewed Marten Mickos. Marten was the CEO of MySQL, now he is the senior vice president of the database group within Sun.

Interesting question about MySQL scalability:
Guy: Is there a theoretical limit of MySQL in case a small business uses it and sales/transactions/whatever explode?
Marten: Every software product has its limits, but I think we have shown that MySQL can scale enormously. Google runs its entire ad system on MySQL. Nokia runs mobile phone networks on MySQL. runs all their business transactions on MySQL. If a small business reaches those limits, it is not a small business any longer--it is an enormous global player.
I am a fan of MySQL myself.

Good to know that FaceBook also uses MySQL (with it's 65 million users), and YouTube used MySQL and Twitter uses MySQL (Scaling Twitter: Making Twitter 10000 Percent Faster).

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Wednesday, March 19, 2008

TaffyDB - A JavaScript DB worth trying out

I recently read about TaffyDB, tried it today. Seems like a handy tool. I would like to use it. TaffyDB is a JavaScript Database, something that can be used for offline data processing in my opinion. For example, a relevant use case is I would like to cache a large report on my browser side and present different views by querying the TaffyDB (I would not like to make server side calls).

It seems like previous attemps have been made for a JavaScript database, a few example are - JavaScript SQL Database with Permanent Storage, Simple JavaScript Database, etc.

TaffyDB is pretty simple to use. Seem feature rich - Under 10K, CRUD Interface (Create, Read, Update, Delete), Sorting, Advanced Queries etc.

Code is pretty easy to write too. Pretty cool, check it out.

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Saturday, March 15, 2008

Leadership is influence ...

Stephen Covey writes about Gandhiji's leadership, excellent paragraph on leadership that I read recently:
"People think that leadership is a position. It isn’t. Leadership is influence. The key to influence is what we’re talking about. You can have influence without position. So don’t be so dependent upon position or formal authority, but use your moral authority, what you know is right."
Read more here.

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Monday, March 10, 2008

Internet Explorer 8: My Top 10 list

IE8 has a bunch of really nice features. I read a few reviews (here and here) and made my ‘Top 10’ list, read on …

  1. AJAX Back Navigation enables users to navigate back and forth without leaving the AJAX application and could be used navigating a page without performing a traditional full navigation. This allows websites to trigger an update to browser components like the address bar by setting the window.location.hash value, firing an event to alert components in the page and even creating an entry in the travel log.
  2. DOM Storage is a simple-to-use method for storing and retrieving strings of key/value pair data. Data can be stored per tab instance for a session or persisted to the local machine. This allows pages to cache text on the machine which reduces the effect of network latencies by providing faster access to pre-cached data. Several innovative uses are possible. For example, use this in combination with the new network connectivity event to allow a page to cache data if it detects that the computer is offline.
  3. Six connections per host instead of two for broadband scenarios and a scriptable property allow for more improved performance by allowing parallelization of downloads in Internet Explorer 8. In addition, this increases functionality by ensuring a request is not blocked to a host if two connections already exist. Websites can optimize their downloads based on a scriptable property.
  4. WebSlices - WebSlices is a new feature for websites to connect to their users by subscribing to content directly within a webpage. WebSlices behave just like feeds where clients can subscribe to get updates and notify the user of changes. A WebSlice is a portion within a webpage that is treated like a subscribe-able item, just like a feed. To enable a WebSlice on your website, annotate your webpage with class names for the title, description, and other subscribe-able properties.
  5. Offline Events - This is an easy way of detecting connectivity within the confines of JavaScript. With it we can write graceful offline Ajax applications. Firefox 3 and IE 8 appear to be the only browsers to support this feature.
  6. Cross-domain Request (XDR) - XDomainRequest, is the easiest way to make anonymous requests to third-party sites that support XDR and opt in to making their data available across domains.
  7. Cross-document Messaging (XDM) APIs allow communication between documents from different domains through IFrames in a way that is easy, secure and standardized.
  8. Facebook Integration: Microsoft capitalized on their partnership with the popular social networking site, Facebook, to allow IE8 users the ability to get status updates from Facebook right from their browser toolbar.
  9. eBay Integration: Like Facebook, this feature also uses IE8's new technology, called "WebSlices", which introduces a new way to get updates from other sites via the browser itself, without having to visit the web site.
  10. Firebug for Internet Explorer - We finally have a heavily-Firebug-inspired tool inside Internet Explorer. To quote Joe Hewitt (creator of Firebug): "I couldn't be happier that Microsoft completely copied Firebug for IE8." I have to agree - a tool like this has been a long time coming and it's greatly appreciated. Only the Internet Explorer team would've ever been the ones to build this tool - there's simply too much information here that's unavailable to typical IE extensions.
  11. Browser mode toggling - At first glance this feature makes the most sense for seeing if your IE 7 page will work ok in IE 8. In actuality, however, this will end up being very useful for developing a standards-compliant page (in IE 8, FF, Safari, Opera) and then toggling to see what the result is like in IE 7. This is so much better than the IE 6 to IE 7 jump where you have to keep your browser in a virtual machine in order for it to run side-by-side (according to Microsoft, at least - even though there were standalone solutions).

Read more at the Microsoft IE8 readiness site.

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Sunday, March 09, 2008

CAPTCHA is Dead, Long Live CAPTCHA!

Interesting post on coding horror. 3 of the most well known CAPTCHA's are now broken - Google, Hotmail and Yahoo!

Wisdom comes from Gunter Ollman, he notes:

CAPTCHAs were a good idea, but frankly, in today's profit-motivated attack environment they have largely become irrelevant as a protection technology. Yes, the CAPTCHAs can be made stronger, but they are already too advanced for a large percentage of Internet users. Personally, I don't think it’s really worth strengthening the algorithms used to create more complex CAPTCHAs – instead, just deploy them as a small "speed-bump" to stop the script-kiddies and their unsophisticated automated attack tools. CAPTCHAs aren't the right tool for stopping today's commercially minded attackers.

Read more here.

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