i have web application built on __asp.net 4.5__
i use ajax control toolkit version __4.0__ for various purpose.
while using the __HtmlEditorExtender__ upon the textbox the toolbar icons on the editor control shows perfectly.
however when on the same application i update the ajax control toolkit version to 4.5 (__4.5.7.123__) the icons on the toolbar does not get displayed as shown below

Comments: Unfortunately, the image you attached is not shown on my side. However, from your description, I assume that the HtmlEditor's icons are not displayed properly. This problem is no longer reproducible in the new version of AJAX Control Toolkit. I suggest you upgrade to it. I am looking forward to your results.
i use ajax control toolkit version __4.0__ for various purpose.
while using the __HtmlEditorExtender__ upon the textbox the toolbar icons on the editor control shows perfectly.
however when on the same application i update the ajax control toolkit version to 4.5 (__4.5.7.123__) the icons on the toolbar does not get displayed as shown below

Comments: Unfortunately, the image you attached is not shown on my side. However, from your description, I assume that the HtmlEditor's icons are not displayed properly. This problem is no longer reproducible in the new version of AJAX Control Toolkit. I suggest you upgrade to it. I am looking forward to your results.