解决关闭showModalDialog窗口弹出画面问题

弹出窗口后，为了不让队父窗口进行操作，使用了window.showModalDialog()的方法，可是在关闭showModalDialog窗口的时候，总是会弹出一个新窗口。开始一直认为这个IE的bug，后来才发现自己在页面上少写<base target="_self">。索性把target属性查个到底：
Syntax

HTML	<ELEMENT TARGET = sTarget... >
Scripting	object.target [ = sTarget ]

Possible Values

sTarget

String that specifies or receives one of the following values.

name	The name of the target window or frame.
_blank	Load the linked document into a new blank window. This window is not named.
_media	Load the linked document into the HTML content area of the Media Bar. Available in Internet Explorer 6 or later.
_parent	Load the linked document into the immediate parent of the document the link is in.
_search	Load the linked document into the browser search pane. Available in Internet Explorer 5 or later.
_self	Default. Load the linked document into the window in which the link was clicked (the active window).
_top	Load the linked document into the topmost window.

The property is read/write. The property has a default value of _self.

Expressions can be used in place of the preceding value(s), as of Microsoft® Internet Explorer 5. For more information, see About Dynamic Properties.

Remarks

If there is no existing window or frame with the same name as specified in the target, a new window is opened with a name equal to the value of the target.
The window name is an optional argument in the open scripting method.

The property is read/write. The property has a default value of _self. 这句话说明默认的时候_self，为什么一定要加上后才有用呢？以后有时间再去研究吧。