Kartris must have the correct file permissions to write to the Images, Uploads and Plugins folders. If it doesn't have the correct permissions to write to these folders you won't be able to upload product images via the Kartris backend, and use other features of Kartris.
If you get permissions errors on shared hosting, you will have to check any control panel you have, to see if you can set 'write' permissions for the folders required. If you don't have this facility, contact your host's support desk and ask if they can adjust these permissions for you.
If you have your own server or are working locally, then you can set these permissions yourself. The first thing is to identify which user your web site runs as. This varies depending on your version of Windows, but typically will be as follows:
Windows XP Pro / Windows Server 2003 (IIS 6): ASPNET
Windows Vista (IIS 7): NETWORK SERVICE
Windows 7 / Windows Server 2008 R2 (IIS 7.5): IIS APPPOOL\[application pool name]
In IIS 7.5, you can check the site's properties to see the name of the application pool. On Windows Server, a new app pool will typically be created for each site, so the user would be something like IIS APPPOOL\www.sitename.xyz. On a local server, you tend to create webs as subfolders of the Default site in IIS, and map them to an existing application pool such as IIS APPPOOL\ASP.NET v4.0.
In Windows Explorer, navigate to the folder holder your Kartris web, and right click on the Images folder. A dialog will appear.
Select the 'security' tab, then click to 'edit' permissions.
Click to 'add' a new user.
If adding ASPNET or NETWORK SERVICE (Windows XP/Vista), you can click 'Advanced' and then 'Find now' and choose the user from the list.
If adding IIS APPPOOL\[application pool name] (Windows 7 / Windows Server 2008), you have to type in the user in full (e.g. 'IIS APPPOOL\ASP.NET v4.0', as it is a virtual user account and won't show up in searches.
Finally, select the account you've just added when it appears in the first dialog, and check the 'full control' box, and save.
We have tested with Windows 8 (IIS 8.0) and it works in the same way as for Windows 7.