Hi @erosaxie
That's a problem in the screen.
You have two choices:
Leave it as is and learn to live with it and hope it doesn't get any worse or replace the screen.
If you decide to replace the screen, here's the [http://h10032.www1.hp.com/ctg/Manual/c05271036.pdf|maintenance and service guide] for the laptop.
Go to p.45 to view the procedure to remove/replace the LCD panel.
You need to check for the HP part number printed on the back of the LCD panel (if possible) to make sure that you're getting the correct part, as depending on what particular variation of the model you have, there are two part numbers shown at the top of p.45 (raw display panel) and two entirely different part number on p.73.
Here's an image showing what features each of the part numbers depict.
Once you have determined the correct part number for your model, search online for the ''part number only'', to find suppliers that suit you best.
[image|3331294]
(click on image)