Should i be worried if my husband searchs for his ex on facebook?

by Suzie
(Fiji)

Should i be worried if my husband searchs for his ex on facebook?

I accidentally caught my husband checking out a profile with an unfamiliar name and upon inquiring persistently he said it was his ex's profile and that she wanted to be friends.

But later I found out from his messages that it was he who requested to be friends.

He always changes the subject when asked about this.

What should I do? Is this serious?