Frequently Asked Questions

1. Why are you giving it away for free?
2. How can I contribute to Open Thumbshots?
3. Can commercial sites use Open Thumbshots?
4. Can I use thumbshots if I don't use the DMOZ directory?
5. Do I need to put the thumbshots attribution?

Technical

1. Can you help integrate thumbshots into my site?
2. Can I pull individual thumbshots directly from your site?
3. Will thumbshots slow down my site?
4. Why are thumbshots 120 x 90 pixels?
5. How often are thumbshots updated?
6. How to enable thumbshots with Norton Internet Security?
7. Why are some thumbshots 1 x 1 pixel?
8. How do I remove thumbshots?
9. Why are some thumbshots not available?
10. What is the thumbshots robot user-agent string?
11. How do I encode the URL value in the querystring?
12. What do you no longer support Static Integration?
13. What are the requirements for server-side caching?

Answers

Why are you giving it away for free? [ TOP]

First of all, we believe picture previews can improve the accuracy of search and directory listings because it exposes the actual content of the site and not just some made up description or title by the webmaster or editor. Thumbshot also increases productivity and reduces frustration because it helps avoid visiting unwanted sites.

We believe the Open Directory Project is one of the most promising community projects on the Internet. Over the years, it has contributed to millions of users in more ways than we can imagine. In short, we would like to contribute back to the DMOZ Open Directory and at the same time educate people on the importance of previews.

How can I contribute to Open Thumbshots? [ TOP]

Creating and distributing thumbshots require large amounts of resources. We are always looking for mirror sites to store our data dumps. We are also looking into other areas where users can contribute. For now, you can help promote Open Thumbshots by using it on your site and telling other users.

Can commercial sites use Open Thumbshots? [ TOP]

Yes, Open Thumbshots is available to everyone including commercial sites. Please see the attribution and license sections for more information.

Can I use thumbshots if I don't use the DMOZ directory? [ TOP]

Absolutely! You can use free thumbshots in your site even if you don't operate the DMOZ Open Directory. We currently provide free thumbshots for any link that appears in the DMOZ Open Directory only. We do offer a commercial solution where every link is available and can be purchased reasonably at http://www.thumbshots.com.

Do I need to put the thumbshots attribution? [ TOP]

Yes, you must put the thumbshots attribution on every page that are hosting thumbshots. You are not allowed to modify the thumbshots attribution.

Can you help integrate thumbshots into my site? [ TOP]

There are free and paid commercial services out there that can help integrate thumbshots into your site. Dominion-Web offers free and pro version software that can do exactly this. phpODP and Engine-Promotion also offer the directory service with thumbshots. There are other software and you can find them by searching the Web.

Beyond this, you can try sending an email to us and we will try to help.

Can I pull individual thumbshots directly from your site? [ TOP]

Yes, you may pull using dynamic integration.

Will thumbshots slow down my site? [ TOP]

Thumbshot is very small in size, about 3kB, and can be downloaded quickly. In fact, thumbshots are helpful for users running on slow modem because users see where they are going and do not waste their time clicking to undesirable sites.

Why are thumbshots 120 x 90 pixels? [ TOP]

A study conducted by University of Calgary shows the level of recall for a previously visited site increases almost linearly with size and levels off at 120 pixels for thumbnails. Thumbshots are 90 pixels in height because 120 x 90 matches the screen resolution in proportions (640 x 480, 800 x 600 etc.). Afterall, most web pages are designed to fit the screen size first. In reality, we can create thumbshots of any size but 120 x 90 is logically the optimal size for previewing web sites. Any smaller or bigger will have impact on usability and download time.

How often are thumbshots updated? [ TOP]

Thumbshots can be updated as often as needed at our discretion. Our policy is to deliver a What You See Is What You Get experience. For the Open Thumbshots Project, we try to update once a month on "active" sites. Updating too frequently will unnecessarily waste resources that can be put to use for other sites. Most sites hardly change or the change is too subtle for the eye to detect (eg. the change of a date on a page is not visible to the eye). Our robot automatically determines whether a particular site should be updated more or less frequently depending on the activity of that site. There are several knobs we can tweak. With time and experience, the robot will adjust to optimally match a site's activity. Please be patient or send a friendly e-mail to us if you think a site is not getting updated often enough and we'll see what the robot thinks.

How to enable thumbshots with Norton Internet Security? [ TOP]

If you are running Symantec Norton Internet Security, thumbshots may not appear on your browser because of the ad blocking function. To enable thumbshots, please refer to the instructions in these two articles:

• How to create a rule to override ad blocking
• Cannot see all of a web page when NIS or NPF is installed

You will need to add a string "thumbshots" for the site "thumbshots.org" to tell Norton Internet Security to enable thumbshots images to appear.

Why are some thumbshots 1 x 1 pixel? [ TOP]

If the thumbshot for the particular URL does not exist or is empty (file not found, connection timeout, invalid request error, etc.) then the thumbshot returned will be a 1 x 1 transparent pixel. If you need to force every thumbshot to fill the 120 x 90 pixel space, you can simply wrap each thumbshot with a borderless table cell of that size.

How do I remove thumbshots? [ TOP]

You can disallow thumbshot of your page by using robots exclusion.

Why are some thumbshots not available? [ TOP]

We currently provide thumbshots for links that appear in the DMOZ Open Directory. If your site is not listed in DMOZ, then we do not support it at thumbshots.org. We do offer a commercial solution where every link is available and can be purchased at http://www.thumbshots.com. If you are interested to have a thumbshot of your site included in the open thumbshots.org database, please fill this form.

Certain thumbshots may not appear because the site is no longer available (404 File Not Found, 400 Bad Request, etc.) or because the webmaster of that site has explicitly requested not to be included using the robots exclusion rule.

Another reason why a particular thumbshot may not appear is because we try to synchronize our thumbshots update against the DMOZ RDF dump, which comes out every few weeks. Therefore, new links that recently got included into DMOZ will not appear immediately. Our commercial solution is more updated and do not require manual synchronization.

What is the thumbshots robot user-agent string? [ TOP]

Currently we use the standard Internet Explorer user-agent string. We have yet to come up with a cooler name!

How do I encode the URL value in the querystring? [ TOP]

You need to encode the URL value before passing to the querystring because your string might conflict with special characters in the URL intended for the browser and the web server. Make sure your URL is fully qualified with the full http:// or https:// scheme at the begining of the URL.

For PHP, you can use the urlencode() function. In Perl, you can use the URI::Escape module or the regex below:

$URL =~ s/([^a-zA-Z0-9_.-])/uc sprintf("%%%02x",ord($1))/eg;

For ASP/VBScript, you can use the Server.URLPathEncode() method. For ASP.NET/C#, you can use System.Web.HttpUtility.UrlEncode() method.

Why do you no longer support Static Integration? [ TOP]

We previously supported the Static Integration by packaging thumbshots into downloadable files and CDs once a month. Doing so prevented us from updating the DMOZ thumbshots more frequently than we would like to. As of April 2004, we no longer support the Static Integration and existing users are asked to use the Dynamic Integration. The Dynamic Integration is easier to integrate and allow you to get updates automatically without needing to download. In fact, 98% of our users use the Dynamic Integration because of the simplicity. We apologize for the inconvenience but it is necessary to provide the best possible service.

What are the requirements for server-side caching? [ TOP]

Thumbshots are normally served from our servers to end-users directly and is the recommended way to implement thumbshots. Server-side caching is used to temporarily store a copy of the thumbshot on your server so that requests are served from you to end-users. You don't and shouldn't need server-side caching to display thumbshots on your site. This topic is for those limited individuals who absolutely need to store a copy of the thumbshots of their server.

In order to perform server-side caching you will need to write your own caching code and lots of disk space. Please make sure that your caching code can understand HTTP redirection when pulling the thumbshot from our server. Also, please be considerate and pull the thumbshots at infrequent intervals to avoid overloading our servers.

We do not encourage server-side caching because any changes in our system (architectural improvements, etc.) may unexpectedly affect your ability to cache. Since each server-side cache implementation varies from individual to individual, it is difficult for us to know or test if our changes will impact your caching system.