In this article we will discuss about customizing newitem.aspx page in SharePoint designer.
Step1: Open your site in SharePoint designer.
Step2: Select your list on the left side in the tree view, expand it, copy NewForm.aspx and paste at same place.
Step3: Open that page and default the "PlaceHolderMain" webpartzone to its default content.
Step4: Using a similar smart tag, do "Create Custom Content" for "PlaceHolderMain".
Step5: In Menu, go to Insert > SharePoint Controls > Custom List Form. Select your list from dialog box.
You will see your same form like on newform.aspx but now In HTML Editable mode. You can add, remove, customize whatever you want, and then save.
Step6: This is not done yet! To use this custom NewForm aspx page, you need to change property of the list. Right click on your list in SharePoint designer, choose Properties, and go to Supporting Files.
Step7: Click on "Browse" and select your custom form for your form type. Click Apply (must) then OK.
Step8: Go to the browser, and add a new list item. You will see your customized newform.aspx page.
Step9: You can create as many pages and different views as you want and user with that page URL will see that custom page.