I bought the wilton decorator tub of icing .  I have used it may times. I opened it and there is a little bit of liquid. Has anyone experienced this. Is it safe to use?

It sounds as though it separated a little bit.  Has it been refrigerated?  If not, does the package say to refrigerate after opening?  If it has been stored properly, it should be perfectly fine to just mix the liquid back into the frosting.

Unless it has changed formulas I don't see it spoiling.  Most likely it is oil seperation.  As Sandra said if you have stored it properly it should be perfectly fine.