An exception is thrown when the page is loaded, if a data table use @form in
onRowSelectUpdate and/or onRowUnselectUpdate attributes:
  <ace:dataTable id="dataTable"
                                         var="record"
                                         value="#{myBean.listWithRecords}"
                                         rowIndexVar="rowNo"
                                         rowStyleClass=" #{myBean.applyCSS(record.selected)} "
                                         selectionMode="multiple"
                                         style="font-size: 14px; text-align: center;"
                                         onRowSelectUpdate="@form"
                                         onRowUnselectUpdate="@form">

Stack Trace:
type Exception report

message

description The server encountered an internal error () that prevented it from fulfilling this request.

exception

javax.servlet.ServletException: Component form needs to be enclosed in a form
javax.faces.webapp.FacesServlet.service(FacesServlet.java:422)
org.netbeans.modules.web.monitor.server.MonitorFilter.doFilter(MonitorFilter.java:393)
root cause

javax.faces.FacesException: Component form needs to be enclosed in a form
org.icefaces.ace.util.ComponentUtils.formatKeywords(ComponentUtils.java:214)
org.icefaces.ace.util.ComponentUtils.findClientIds(ComponentUtils.java:227)
org.icefaces.ace.component.datatable.DataTableRenderer.encodeSelectionConfig(DataTableRenderer.java:1192)
org.icefaces.ace.component.datatable.DataTableRenderer.encodeScript(DataTableRenderer.java:459)
org.icefaces.ace.component.datatable.DataTableRenderer.encodeEntierty(DataTableRenderer.java:529)
org.icefaces.ace.component.datatable.DataTableRenderer.encodeEnd(DataTableRenderer.java:440)
javax.faces.component.UIComponentBase.encodeEnd(UIComponentBase.java:875)
javax.faces.component.UIComponent.encodeAll(UIComponent.java:1763)
javax.faces.render.Renderer.encodeChildren(Renderer.java:168)
org.icefaces.impl.renderkit.RendererWrapper.encodeChildren(RendererWrapper.java:54)
javax.faces.component.UIComponentBase.encodeChildren(UIComponentBase.java:845)
javax.faces.component.UIComponent.encodeAll(UIComponent.java:1756)
javax.faces.component.UIComponent.encodeAll(UIComponent.java:1759)
javax.faces.component.UIComponent.encodeAll(UIComponent.java:1759)
com.sun.faces.application.view.FaceletViewHandlingStrategy.renderView(FaceletViewHandlingStrategy.java:401)
com.sun.faces.application.view.MultiViewHandler.renderView(MultiViewHandler.java:131)
com.sun.faces.lifecycle.RenderResponsePhase.execute(RenderResponsePhase.java:121)
com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101)
com.sun.faces.lifecycle.LifecycleImpl.render(LifecycleImpl.java:139)
javax.faces.webapp.FacesServlet.service(FacesServlet.java:410)
org.netbeans.modules.web.monitor.server.MonitorFilter.doFilter(MonitorFilter.java:393)

If @form is replaced with @this the page loads normally.