we have a sales profile ,when I login as sales user I am not able to see Today tab on Ipad in salesforce1
The first item you add to the navigation menu list becomes your users' landing page, so if the Today's view is first, the first thing the users will see when they log in is the Today's view.
The navigation menu configuration you will set will apply to all users in your org, however they will see only the items their profiles permit them accessing.
You may not want to make the Salesforce1 menu exactly the same as the order of your Web App tabs, instead try to put the items that users will want to access most at the top. Anything you place below the Smart Search Items element will appear in the Apps selectoin of the navigation menu.
For additional information on how to customize the Navigation Menu please refer to chapter 6 in the Salesforce1 Developer Guide.