Bug 286949 [Browser] Bad usage of URL#equals(Object) in WebBrowserEditorInput
HEAD WebBrowserEditorInput#equals(..) calls URL#equals(Object), but the latter resolves the host of the URLs via DNS lookups, which is most of the time not what you want. You should instead compare the strings from URL#toExternalForm(). Furthermore, WebBrowserEditorInput should also override hashCode() (equal objects must have equal hash codes). Note that URL#hashCode() is also broken, so you should use URL#toExternalForm() there as well.
bundles/org.eclipse.ui.browser/src/org/eclipse/ui/internal/browser/WebBrowserEditorInput.java
* Saves the state of an element within a memento.
	 * 
	 * @param memento
	 *            the storage area for element state
	 */
	public void saveState(IMemento memento) {
		memento.putInteger(MEMENTO_STYLE, style);
		if ((style & IWorkbenchBrowserSupport.PERSISTENT) != 0 && url != null) {
			memento.putString(MEMENTO_URL, url.toExternalForm());
		}
		if (id != null) {
			memento.putString(MEMENTO_ID, id);
		}
		if (name != null) {
			memento.putString(MEMENTO_NAME, name);
		}
		if (tooltip != null) {
			memento.putString(MEMENTO_TOOLTIP, tooltip);
		}
	}
	/**
	 * Converts this object to a string.
	 * 
	 * @return java.lang.String
	 */
	public String toString() {
		return "WebBrowserEditorInput[" + url + " " + style + " " + id + "]";  
	}
}