is it fine to surf porngraphy material alone?

To each its own. There is no such thing as right or wrong for most things. It depends to what philosophy you prescribe in your marriage. I have friends who are married with kids and believe in things like open marriages, escort services etc, more power to them. Their life, if both Husband and Wife agree to it, then why does my opinion even matter? In my marriage, I am a lot more traditional - I like the concept of one man and one woman, madly in love with each other and who are best friends who could do anything together - including watch porn, crack the most inappropriate jokes in front of each other and share our deepest, darkest fears. But being best friends also means giving each other Space and alone time to do things separately. So hubby can choose to watch porn in front of me, together with me, or alone far away from me, and I really would not care.