XUL:Attribute:persist

persist: Type: space-separated list of attribute names; A space-separated list of attributes that are maintained when the window is closed. When the window is re-opened, the values of persistent attributes are restored. In Mozilla, persistent attributes are stored in the per-profile file localstore.rdf. Persistence can also be stored using the document.persist function. In order for persistence to work, the element must also have an id.

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