While testing one of our applications recently we discovered that every page in the application was being requested twice. For most of the application this did not cause any noticeable problems. However there was one area where this caused a huge problem.. processing customer credit cards!

This behaviour only occurred in Firefox. Initially we thought it was related to the browser plugins… Firebug or some other Firefox extension or perhaps some client side JavaScript event that was fired twice. But despite disabling JavaScript and removing all extensions, each page was still being requested twice by the browser.

After a bit of digging around it turns out that in some circumstances, when you have empty src attributes or hrefs, Firefox will request the page again. Checking the source we discovered an empty href! On the face of it, this may seem like a bug in Firefox, but it turns out that this actually the correct behaviour as defined in RFC3986. It looks like Firefox is one of the few browsers that actually implements the standard correctly!

I love the Amazon Kindle. It’s a great bit of kit and the screen is awesome for reading, even in the sun. It’s light, can fit in my jacket pocket and is even small enough to hold on the tube in one hand. No more trying to turn the pages on one of those huge Wrox books while crammed into a coffin sized space during rush hour on the misery line! I find myself reading on the Kindle more than on the iPad (although I still once in a while find myself touching the screen of the Kindle to scroll ). However it is obscene the pricing of the Amazon e-books and it’s enough for me to warn people off buying a Kindle. Take for example Don Norman’s excellent, the design of Everyday things. On Amazon.co.uk the book is currently being sold for £7.90. So how much would you expect the e-book version to be £2.99? £1.99. No, The Kindle edition is currently £6.98. That is a difference of less than a pound!

Remember the book has already been written, there are no additional costs for storage or delivery and while it costs some money to have a book converted to the correct format, this can be done by any good company for less than £100. There is simply no justification for the high price of Kindle books. A trades body somewhere needs to take a good look at this.

The success of iTunes is partly down to the ability for people to buy just the songs they want for less than a pound as opposed to having to shell out £10+ for an album when you only want 2 or 3 tracks. I can see an explosion in illegal e-book download sites on the horizon which would be a shame and would undermine the hard work put in by the authors.

I would strongly suggest you think twice about buying a kindle until the prices of the books come down. Also check that the books that you want to buy or that are on your wish list are actually available. Disappointingly, there are a huge number of books which are not yet available on the Kindle.

So Spotify are set to limit their free service. I don’t think this is a bad thing from a business perspective, particularly if they have to pay the record companies every time a free user plays a song. A paid service is better than no service! However if you’re part of a family that all uses Spotify, it is handy having a free service that the rest of the family can use. The problem with the existing paid version is that only one device can play music at any one time.  On the face of it this may not seem like such a problem. Until you’re out listening to Spotify on your phone and your service is interrupted because someone at home has started up the family machine or you’re in the office happily listening away to Bob Marley’s greatest hits and suddenly it stops playing and informs you that Spotify is playing elsewhere. While I am happy to pay for the premium service, I think having to pay for additional subscriptions is probably a bit much in this time of austerity. I understand why this restriction is in place, you wouldn’t want people who have subscribed to the premium service sharing their accounts with the whole world. But there has got to be an acceptable halfway. Perhaps limiting the service to playing on 2 authorised devices at the same time. So Spotify if you’re listening (no pun intended), what we really want is a family version!!

I’d love an iPhone application that would do different things based on who is calling. So if the wife was calling, the phone would ring but if someone from work was calling (during the weekend) the phone would return a pre-recorded message. If I was in a meeting and a friend called it would go straight to voicemail but send them an SMS message informing them that I’m in a meeting. This isn’t currently possible due to limitations in the APIs.

This would be really handy for those very rare occasions when a Spurs fan rings me after my team has just lost a game, when they call the phone would simply switch off.

New year a new blog! My blog has been lacking some care and attention but one of my resolutions is to get back into regular blogging stay tuned!

One of the things that took me a while to work out how to do when I first switched to a Mac from a PC a few years ago, was how to simply create an empty text file. Of course on OSX you have stickies but sometimes you want to create a new plain text file in a particular folder. So for those new to OSX: Open a terminal window and drag the folder you want to create the file inside into the terminal window, this will automatically switch to the directory of the folder in terminal. Then enter "touch filename.txt" that's it…almost as easy as right clicking and selecting "create new file …"

I've been watching the rise of the ebook reader with interest, particularly as Apple are rumored to have one in the works. The reason it is of particular interest to me is because I do a lot of reading while commuting. If you use London Underground to get to work then you'll know that in cramped carriages during rush hour it can be difficult to flip through one of those huge Wrox or Apress books. iPhone to the rescue!. O'Reilly Safari used to provide an iPhone app that allowed subscribers to download a couple of chapters of a book on your O'Rielly bookshelf to your phone. Unfortunately they have replaced this with an application which requires internet access. Which is no good if you're underground!. That's when I found Instapaper. My favourite app of the moment. It's very simple, you have a button on your browser – you click read later and then hit an update button on your iphone it begins to download the pages to your phone (with or without images). Great for that arduous commute after work on the way home.

Which brings me on to ebook readers. What I would really love is an ebook reader which allows me to read through digital copies of books I already own. When I purchase books from Amazon (or somehwere else) I would love the option to buy an ebook version as well (or instead of). The up and coming ebook reader Nook from Barnes & Noble which runs the Android OS is rumored to allow you to do this. I'd absoloutely love a light ebook reader which I can hold in one hand, turn pages with one hand, has a decent screen, allows me to download books or load my own books. I would also like it to allow me to read word docs, pdfs etc. and bookmark or annotate them. The key thing here however is to be able to download and read anybook I purchase (as opposed to the limited libraries some of the ebook reader vendors make available). From this comparison it seems that we are almost there..

I just came across a really useful site for generating invoices online: www.invoicemachine.com. The site has a nice clean design and despite a few minor usability issues it's easy to use. It allows you to provide a link to an invoice online, track the history of an invoice and add payments. It also has an API so you could integrate it directly with say your issue tracking system for example.