YHX,
Open your DNN web.config, and find the CuteEditor section and set UseDNNDefaultWidth="true".
<add name="CEHtmlEditorProvider"
type="DotNetNuke.HtmlEditor.CEHtmlEditorProvider, DotNetNuke.CEHtmlEditorProvider"
providerPath="~\Providers\HtmlEditorProviders\CEHtmlEditorProvider\CuteSoft_Client\CuteEditor\"
UseDNNRoleASFileNamePrefix="true"
UseDNNRootImageDirectory="true"
RemoveServerNamesFromUrl="true"
UseDNNDefaultWidth="true"
asp.net Chat http://cutesoft.net/ASP.NET+Chat/default.aspx
Web Messenger: http://cutesoft.net/Web-Messenger/default.aspx
asp.net wysiwyg editor: http://cutesoft.net/ASP.NET+WYSIWYG+Editor/default.aspx
asp wysiwyg html editor: http://cutesoft.net/ASP
asp.net Image Gallery: http://cutesoft.net/ASP.NET+Image+Gallery/default.aspx
Live Support: http://cutesoft.net/live-support/default.aspx