Common issues for users of IE6+ is image caching. All version of IE6 share this issue - the same image can be fetched from server multiple times ( based on server response and settings of browser ), such can cause can cause performance issues for both server and client.
Starting from dhtmlxTree 1.5, special image loading mode available, it can be enabled by tree.enableIEImageFix(true); In such mode IE load images through CSS, instead of native IMG elements. As result problem solved for most version of IE6 ( still can occur in some version of IE6 SP1 )


Benefits of "IE Image Fix" mode

1. Images cached on client
2. About 1.5 times loading speed improvement in FF

Disadvantages of "IE Image Fix" mode

1. About 1.5 times loading speed decreasing in IE