InitializeConnectionScript

// Map the cookies in the current document in an array
// of cookie values, keyed on each's cookie name

var cookies = [];
var crumbs = document.cookie.split("; ");

for (var i = 0; i < crumbs.length; i++) {
    var crumb = crumbs[i];
    var assignmentPos = crumb.indexOf("=");

    var name = crumb.substring(0, assignmentPos);
    var value = crumb.substring(assignmentPos + 1, crumb.length);

    cookies[name] = value;
}

// Assume that connection.js is already included

sforce.connection.sessionId = cookies["sid"];