webresource.axd

if there is a treeview created for a web part by visual studio 2005, the node icon might not be there.

Reason/Solution:
(from Jan Tielens, http://weblogs.asp.net/jan/archive/2005/11/24/431425.aspx)

Many of the default ASP.NET 2.0 controls use this feature to store scripts and images, a good example is the TreeView control. If you want to use the same technique in SharePoint

The problem is that the ISAPI filter of SharePoint will try to process the request to WebResource.axd, so you won’t be able to retrieve any resources.

To prevent that the ISAPI filter will try to process the requests to WebResource.axd, you have to exclude it as a managed path. On your SharePoint server, open up the SharePoint Central Administration site from the Administrative Tools start menu group and click the “Configure virtual server settings” link. On the next page you will see a list of all your virtual servers, click on the one that you would like to configure (you have to repeat the steps for each virtual server). Next, click the “Define managed paths” link. In the “Add a New Path” section, fill out WebResource.axd as the name of the path, for the type select “Exclude path”. Finally click the OK button. Now you can use WebResource in SharePoint sites!