Have only one button submit form?

I have inherited a project and there is a form with 3 buttons:

<input type="submit" id="ctl00_contentPlaceHolder_back" value="Make Changes" name="ctl00$contentPlaceHolder$back" onClick="history.back();">
<input type="submit" id="开发者_开发问答ctl00_contentPlaceHolder_preview" value="View Outside" name="ctl00$contentPlaceHolder$preview">
<input type="submit" id="ctl00_contentPlaceHolder_submit" value="Send Card" name="ctl00$contentPlaceHolder$submit">

How do I make it so, that only 1 button actually submits the form to another page for processing?

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Change all the other ones to type="button"

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Change the input type="button" instead of type="submit". These kind of look like ASP controls, so find and replace these form buttons with a plain button, unbound.

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By not letting them be submit buttons. Use type="button" instead of type="submit".