I am using Autodesk Inventor Professional - 2011
I would like to know how to customize the drawing title block.

Depending on how much you want to customize the title block, the usual way is to open a drawing, expand the sheet folder in the browser, then right click on the tab just below the border type (ie ANSI-A) and select "edit definition" to enter the sheet editor. You can then delete lines, change dimension parameters, edit or remove constraints, insert text boxes, etc. Don't forget to finish the sketch, and save the edits to default or save the title block as a template for use again.Hope this helpsDave