总之，我发现eclipse IDE中的默认html编辑器不显示概述的结构。似乎IDE只是把html作为简单的文本，所以在我安装后的网页编辑器插件按照https://stackoverflow.com/questions/54868/what-is-the-best-html-editor-for-eclipse的答案成功，当我打开html文件与Web Page Editor，我得到一个错误说：
无法打开编辑器：引发意外异常。

java.lang.NullPointerException
    at org.eclipse.wst.sse.ui.StructuredTextEditor.createModelDependentFields(StructuredTextEditor.java:1305)
    at org.eclipse.wst.sse.ui.StructuredTextEditor.update(StructuredTextEditor.java:2836)
    at org.eclipse.jst.pagedesigner.editors.HTMLEditor.sash_createAndAddDesignSourcePage(HTMLEditor.java:278)
    at org.eclipse.jst.pagedesigner.editors.HTMLEditor.createPages(HTMLEditor.java:439)
    at org.eclipse.ui.part.MultiPageEditorPart.createPartControl(MultiPageEditorPart.java:357)
    at org.eclipse.ui.internal.EditorReference.createPartHelper(EditorReference.java:662)
    at org.eclipse.ui.internal.EditorReference.createPart(EditorReference.java:462)
    at org.eclipse.ui.internal.WorkbenchPartReference.getPart(WorkbenchPartReference.java:595)
    at org.eclipse.ui.internal.EditorReference.getEditor(EditorReference.java:286)
    at org.eclipse.ui.internal.WorkbenchPage.busyOpenEditorBatched(WorkbenchPage.java:2857)
    at org.eclipse.ui.internal.WorkbenchPage.busyOpenEditor(WorkbenchPage.java:2762)
    at org.eclipse.ui.internal.WorkbenchPage.access$11(WorkbenchPage.java:2754)
    at org.eclipse.ui.internal.WorkbenchPage$10.run(WorkbenchPage.java:2705)
    at org.eclipse.swt.custom.BusyIndicator.showWhile(BusyIndicator.java:70)
    at org.eclipse.ui.internal.WorkbenchPage.openEditor(WorkbenchPage.java:2701)
    at org.eclipse.ui.internal.WorkbenchPage.openEditor(WorkbenchPage.java:2685)
    at org.eclipse.ui.actions.OpenWithMenu.openEditor(OpenWithMenu.java:344)
    at org.eclipse.ui.actions.OpenWithMenu$2.handleEvent(OpenWithMenu.java:192)
    at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:84)
    at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1003)
    at org.eclipse.swt.widgets.Display.runDeferredEvents(Display.java:3910)
    at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3503)
    at org.eclipse.ui.internal.Workbench.runEventLoop(Workbench.java:2405)
    at org.eclipse.ui.internal.Workbench.runUI(Workbench.java:2369)
    at org.eclipse.ui.internal.Workbench.access$4(Workbench.java:2221)
    at org.eclipse.ui.internal.Workbench$5.run(Workbench.java:500)
    at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:332)
    at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:493)
    at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:149)
    at org.eclipse.ui.internal.ide.application.IDEApplication.start(IDEApplication.java:113)
    at org.eclipse.equinox.internal.app.EclipseAppHandle.run(EclipseAppHandle.java:194)
    at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:110)
    at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:79)
    at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:368)
    at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:179)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:601)
    at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:559)
    at org.eclipse.equinox.launcher.Main.basicRun(Main.java:514)
    at org.eclipse.equinox.launcher.Main.run(Main.java:1311)
    at org.eclipse.equinox.launcher.Main.main(Main.java:1287)

还弹出一个错误说：

Unsupported content type in editor.
To associate file extension with a supported content type,
Please see Content Type Preference Page.

我还查了Content Type Preference Page下面是设置。请检查它。

以前有人遇到过这个问题吗？谢谢.