Microsoft SharePoint Designer is a specialized HTML editor and web design freeware for creating or modifying Microsoft SharePoint sites and web pages.  SharePoint Designer features focuses on designing and customizing Microsoft SharePoint websites.

What we can do with the SharePoint Designer :

• Creating/editing SharePoint Master Pages and site wide Cascading Style Sheets.
• Changing layout of SharePoint Pages and creating Data View Web Parts and Managing the Web Part Zones.
• Create customized workflows with a set of controls that are not available in the web interface.
• Controlling multiple checked out files in a single interface.
• Manual backups (and restoring) of individual sites in both WSS3 and MOSS 2007

A Web Part zone is a Web Part container that can be configured to control the organization and format of the Web Parts contained in it. By default, the SharePoint page has 2 zones Left and Right:

A web part zone can contain several web parts, but in some cases, the page needs more zones. Adding new zones can be done from the SharePoint Designer.

Insert a Web Part zone in 2007 portal:

1. In Office SharePoint Designer 2007, open the page where you want to insert the Web Part zone.
2. If the Web Parts task pane is not already open, open it by clicking Web Parts on the Task Panes menu.
3. In Design view, click the location on the page where you want to insert the Web Part zone.
4. At the bottom of the Web Parts task pane, click New Web Part Zone.

The new Web Part zone is inserted on the page.

1. Right-click the new Web Part zone, and then click Web Part Zone Properties on the shortcut menu.
2. In the Web Part Zone Propertiesdialog box, do any of the following:
   • Give the zone a title Under General settings, in the Zone title box, type a name for the new zone.
   • Choose a frame style Under General settings, in the Frame style list, click the style that you want.
   • Choose a layout for the zone Under Layout of Web Parts contained in the zone, click either Top-to-bottom (vertical layout) or Side-by-side (horizontal layout).
   • Control changes made in the browser Under Browser settings for Web Parts contained in the zone, select check boxes to allow users to make the indicated changes while they view the page in a browser, or clear check boxes to prevent users from making those changes.
3. When you finish, click OK.

For instructions about inserting Web Parts in your Web Part zone, see the article

http://office.microsoft.com/en-us/sharepoint-designer-help/insert-or-delete-a-web-part-zone-HA010151394.aspx