<p>Can a firefox XPCOM component read and write page content across multiple pages? </p>

<p>Scenario:
A bunch of local HTML and javascript files. A "Main.html" file opens a window "pluginWindow", and creates a plugin using:<br><br>
<code>
netscape.security.PrivilegeManager.enablePrivilege('UniversalXPConnect');<br>
var obj = Components.classes[cid].createInstance();<br>
plugin = obj.QueryInterface(Components.interfaces.IPlugin);<br>
plugin.addObserver(handleEvent);
</code></p>

<p>The plugin that has 3 methods.</p>

<p><code>IPlugin.Read</code> - Read data from plugin<br>
<code>IPlugin.Write</code> - Write data to the plugin<br>
<code>IPlugin.addObserver</code> - Add a callback handler for reading.<br></p>

<p>The "Main.html" then calls into the pluginWindow and tries to call the plugin method Write.</p>

<p>I receive an error: </p>

<p><code>Permission denied to call method UnnamedClass.Write</code></p>

Subversion only stores the delta (differences), between 2 revisions, so this helps saving a LOT of space, specially if you only commit code (text) and no binaries (images and docs).
Additionally I´ve seen a lot of very big projects using svn and never complained about performance.
Maybe you are worried about checkout times? then I guess this would really be a networking problem.
Oh, and I´ve worked on CVS repositories with 2Gb+ of stuff (code, imgs, docs) and never had an performance problem. Since svn is a great improvement on cvs I don´t think you should worry about.
Hope it helps easy your mind a little ;)