Here's how you can add an edit button to your Internet Explorer's toolbar which in turn will call your favorite HTML editor to edit the pages you're viewing:
Go to "View | Options | Programs"
Click on "File Types"
Select "Internet Document (HTML)" and click on edit
If you already see "edit" in the "actions" list, select it and click on "Edit." Otherwise click on "New" and type "edit" in the "Action" input box.
In "Application used to perform action" input box, type the path to your favorite HTML editor followed by a space and a "%1" (include the quotes as well). For example, if you want to make Windows Notepad your web page editor, type:
notepad.exe "%1"
Restart Internet Explorer.