Have you ever been to a web site and seen this?

This warning is triggered in IE if it is displaying a secure HTTPS page that has caused a non-secure (i.e. HTTP based) resource to be downloaded. The message box doesn’t allow the user to control whether the non-secure content should be downloaded, only whether it should be displayed.

This seems rather pointless as the damage may already have been done if the non-secure content was a picture of your passport, bank statement or credit card! However, this is the default setting in IE so it is best to avoid this warning being generated on your web site.

This setting can be changed in IE by:

1. Going  to Tools->Internet Options->Security
2. Select the Security tab
3. Click on the Internet zone icon at the top of the tab page
4. Click the Custom Level button
5. In the Miscellaneous section change Display mixed content to Enable
6. Repeat steps 1 – 5 for the Local intranet and Trusted sites zones

Recently, we saw this warning in the shopping cart of an  computer store,  so we fired up HttpWatch to see what was causing the problem. A quick search for a URL starting with ‘http:’ should have located the request causing the problem:

No HTTP requests were recorded for this page in HttpWatch. So what was causing the ‘Do you want to display nonsecure items’ message?

It turns out that IE warns about HTTP based content even if it was read from the browser cache or the IE image cache. Requests from the browser cache are shown as (Cache) in HttpWatch, but as we previously described access to the IE image cache is not recorded.

The resource causing the warning on this page must have been read from the image cache. We confirmed this by refreshing the page in IE and performing another search:

The refresh forced IE to download all the embedded resources on the page and it became clear that it was the Google Checkout image that was causing the problem. Changing this image’s URL to use HTTPS would prevent the warning from appearing.

Here’s a summary of some recent blog posts that have mentioned HttpWatch:

“My team has been using HttpWatch for a few months now to analyze the client side performance of SkyDrive.  Previously, I had relied on some internal tools we use that are based on NetMon, as well as Fiddler and Firebug with the YSlow plugin.  While these tools were pretty good, here’s why I think HttpWatch beats them all”

from HttpWatch – My favorite web performance tool,

“Inspecting the payload your server is issuing out can be quite tricky, luckily for the likes of you and I the boffin’s at Microsoft created Fiddler and Simtec created HttpWatch (which I use every single day – probably the best developer tool I’ve got in my arsenal, it’s also coincidentally the tool you’ll see screen shots from throughout this article)”

from Pimp my ASP.NET web application – Part One

“Wow, I thought I was good at learning about new tools, but I never heard about HttpWatch … It works much in the same way as Firebug, as a add-in to Internet Explorer. It looks really really cool, and some of the features are even better than Firebug. I like how it even gives you insight into the TCP level of your browsing sessions, such as how much time a DNS lookup takes”

from Httpwatch: Commercial alternative to Firebug for Internet Explorer

“While modifying a website which uses AJAX, we are converting from a rather non-standard implementation of AJAX calls to one that is a lot more standard.  But, we’re still concerned about the number of the objects being downloaded, the size of each object, the time each object takes to download, the number of round-trips, etc. We wanted a way to easily visualize what’s happening. HttpWatch provides a way”

from A New Tool in My Tester’s Tool Box – HttpWatch

“HttpWatch is a great add-on tool to Internet Explorer that captures your IE HTTP traffic. The best part for me is that it can be driven programaticly from my Watir Tests.“

from Using HttpWatch with Watir

Web 2.0 is a term often used to describe next generation web sites that have moved beyond the simple page request->process->response cycle and are utilizing services on the web server to return data that can be rendered without making page transitions. The result is often a more responsive user interface that closely mimics a desktop application.

The technology to make HTTP calls from JavaScript embedded in an HTML page was first introduced for general use by Microsoft in IE5 in order to support Outlook Web Access way back in 1999. However, the XmlHttpRequest object was not widely used until it was adopted by Mozilla in 2002. In 2005 the programming model was given the name Ajax which has now been widely recognised and stands for Asynchronous JavaScript + XML.

From a performance perspective Ajax has two main benefits:

1. It can reduce the number of round trips by minimizing the number of page transitions in a web application
2. It can reduce the size of uploaded and downloaded data because it allows the web programmer to control exactly what is transferred. For example, if a user performs a search the data can be returned in a compact data format (e.g. JSON ) rather than HTML.

In order to illustrate how Ajax can increase the speed and usability of a site let’s first look at a traditional web site and then compare it to an Ajax example.

This is what happens on Expedia.com when we try to book a flight but we specify a partial or mispelled city code. In this case we typed in “LOND” instead of “LON” or “London”. We expectantly press the submit button hoping for a list of possible flights, but instead we’re directed to an error page:

Using HttpWatch we can see that Expedia took 4.4 seconds, 30 round trips and 156K of data (of which 41K was uploaded)  to display the error page:

Even if there are no further mistakes we will still have to make further page transitions before we get the results we’re expecting.

Let’s look at a similar example on BA.COM where Ajax has been used:

Here we did exactly the same thing – typed “LOND” instead of London. Instead of having to press submit, fetch a new choices page (with all linked page components) and drag the user through an additional form, the page used background processing to query the server and display a list of possible choices.

The beauty of this approach is that is that it didn’t require any user interaction, is very fast and it didn’t leave the search page. Here’s the Ajax request in HttpWatch:

BA.COM uses the DWR framework for Ajax to request the possible airports. The framework returns a JavaScript list used to render the content into the dropdown list control. The single HTTP call required is much smaller and faster than the Expedia model where the whole page must be fetched and rendered.

Due to the inconsistencies between the programmable object models on different browsers, most developers now choose a framework to ease JavaScript development and most provide Ajax helper functions that wrap XmlHttpRequest. Java’s DWR has RPC style support. ASP.Net’s Ajax library, Dojo, Yahoo’s YUI and Google’s GWT support a whole suite of UI and control extensions as well as offering some kind of Ajax support. Similarly, Prototype and jQuery are two extremely lightweight and popular JavaScript libraries.

Let’s say you wanted to populate a list box with city codes based on the country a user selects. In Web 1.0 you would have to submit a form making a round-trip to the server with your choice of country so that the server could render the appropriate list of choices on the resulting HTML page.

With Ajax, this can all be done in the background. A lot of services use the XML data format, but there’s no restriction on the content type that XmlHttpRequest can send or receive. It could be HTML, JSON or any other format that the page’s JavaScript can parse.  Here’s an example of using the jQuery library to populate a list control from an Ajax request:

<script type="text/javascript" src="jQuery.js"></script>
...
<h2>Products</h2>
<div id="products">(fetching product list ...)</div>
<script>
...
jQuery("#products").load("productListHTML.aspx");
...
</script>


The products <div> is initially empty, but the load() method wraps XmlHttpRequest and fetches some HTML from the server and uses it to populate the <div>.

One of the drawbacks people found with using Ajax was that they ended up breaking the back button. Clicking the Back button in some Ajax applications did not go to the previous logical operation. For example, if you were viewing the results of a search you would expect Back to take you to the search page so that you could modify the search criteria. Instead, the user would be taken to whatever happened to be the previous page in the browser’s history list.  In some cases, they may even have been the previous web site that the user had visited.

More recently though, browsers have exposed object models to help Ajax applications manipulate the browser history artificially so that they can correct the flow of operations as the user uses the forward and back buttons.