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2.5 Undo, Redo, and the History Panel

One of the great consciousness-altering moments of the twentieth century was the
introduction of the Undo command. After a long day in front of the computer, the
ability to undo any action seems quite natural. (Unfortunately, reaching for the Ctrl+Z
keys after spilling grape juice on Grandma's antique tablecloth still doesn't work in
the real world.)

Fortunately, most steps you take in Dreamweaver can be reversed with either the
Undo command or the History panel.

2.5.1 Undo

Like most computer programs these days, Dreamweaver lets you undo the last step
you took by pressing Ctrl+Z (-Z), or by choosing EditUndo. (This command
changes to reflect your most recent action. If you just deleted some text, for example,
it says EditUndo Delete.) When you're feeling indecisive, you can redo the action
you just undid by choosing EditRedo or by pressing Ctrl+Y (-Y).

Jumping back and forth with the Undo/Redo commands is a good way to compare a change you made to a Web page with its previous appearance. For instance, suppose you're having trouble deciding on a background color for a Web page. You could set it to dark blue, then set it to dark purple, and then choose Edit Undo Set Page Properties to return to the dark blue background. Choose EditRedo Set Page Properties to see the purple background again. This before-and-after toggling feature of the Undo/Redo combo can be great addition to your Web-building arsenal.

You're not limited to a single undo, either. You can undo multiple steps, up to 50 of
them, or whatever number you specify in Preferences. Choose EditPreferences (on
the Mac it's DreamweaverPreferences) to open this dialog box, click the General
category from the Category list, and change the number in the Maximum Number of
History Steps box. (Note, however, that the more steps Dreamweaver remembers, the
more memory the program needs. If you set this preference very high or your computer
doesn't have a lot of memory, you may find your computer acting sluggish.)

You can even undo actions after you have saved a document (although not after you've closed it). Unlike many programs, Dreamweaver doesn't erase the list of actions you've performed when a page is saved. This means you can feel free to save as often as you wanta wise safeguard against crashes and other mishapswithout losing the ability to undo what you've done.

2.5.2 History Panel

You may wonder why the Preferences setting for the Undo command refers to "History
Steps." It's because Dreamweaver creates a history for a document as you work
on it. Each time you add text, insert a graphic, change the background color of the
page, or do anything else to a document, Dreamweaver adds a new step to a list of
previous actions.

All of these steps are listed in the History panel. To see it, choose WindowHistory,
or press Shift-F10.

Each row in the panel represents one action or step, and includes a description. For
instance, hitting Return or Enter while typing in the document creates a step called
New Paragraph. Steps are listed in the order you perform your actions, with the latest
actions at the bottom and earliest action at the top of the list.

The History panel can do a lot more than undo actions. It can also be used for automating
many routine tasks that you perform while building your Web pages. To find out how
to use this feature, see Chapter 19.

But the History panel isn't just a dull document to pore overit's a living, multiplestep
Undo command. Use the History slider to move to any step in the history list. To
undo one action, for example, drag the slider up one step. When you do this, you'll
notice that the slider's previous position step is grayed out. Steps that are dimmed
represent future steps, so moving the slider down one step is the equivalent of choosing
EditRedo.

You can undo or redo multiple steps by moving the slider up or down the list. Alternatively,
you can click on the track to the left of a step to move the slider to that step.

If you want to eliminate all of the history steps for a documentto free up some of
your computer's memory, for exampleselect Clear History from the History Panel's
context menu. But be careful: This is the one action you can't undo.