If you want the value for this choice to be different from the text displayed in the drop-down box itself, select Specify value, and then type the value in the box.
For example, a choice in the menu could be John, but the value returned in the form results could be me.
Click Selected under Initial State if you want the choice to be selected by default when a site visitor first opens the form.
Click OK.
Repeat steps 3 through 6 for each choice you want to add.
To change the order in which choices are displayed, click a choice in the list, and then click the Move Up or Move Down button.
In the Height box, type how many lines of text you want to show in the drop-down box.
For example, if the drop-down box has three options, you can set the height to 3 so that all choices are visible.
Click Yes under Allow multiple selections if you want to allow multiple selections in the drop-down box. If you click No, the site visitor will be able to make one choice only.
Click the Style button to access other options for formatting your form using cascading style sheets as an inline style. "
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"Note To test the functionality of your form, you must first publish your web site to a web server running either the FrontPage Server Extensions or SharePoint Team Services from Microsoft. Ask your web administrator or Internet Service Provider whether this software is installed on your web server. Once the web site is published, click Preview in Browser to test the form."
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If those techniques don't work, you might have to use JavaScript. I'm sure that the experts will say that it's easy but it looks hard to me! :
http://www.pcbest.com/frontpagetips/FrontPageDrop-DownMe nu.htm