When I click on Recent Post item ("Caneine and feline medicine" ) on the right side bar on my site: masaueharadesign.com (I'm practicing WordPress here.), blank space and a dashed line appears on the top in the center column. Please tell me how I can get rid of them.

They don't appear (in the center column) if I click on Categories ("Preventive Medicine") below Recent Post! I'm confused.

Thanks.

That blank space is for the navagation of your posts. Add a couple more posts and wyo will get the titles with arrows pointing right and left. If you have three posts, titled ONE, TWO and THREE, when you get to post ONE you will see

TWO>>

if you go to post TWO you will see

<<ONE THREE>>

and on post THREE you will see

<<TWO

see ATH->Next/Previous Navigation for options