Hi Sheetal,
You need to check "Read Cell Content As" in Format Cell>General Properties and Select "hyperlink" from drop down.
Also, refer to section "4.2.2 Configuring Blank Cells in 4.0 Web Intelligence Reports" in below to configure you blank cells to associate with any blocks and then use the images to make them visible through IPad or mobile.
http://help.sap.com/businessobject/product_guides/boexir4/en/44x_mobiOS_admin_en.pdf
Thanks
Mallik