Is my site being cached? Getting different results.

When I check my blog in “Source View” I get different results on whether it is being properly cached by WP Super Cache or not, as follows:

In Safari: “…Page not cached by WP Super Cache. Check your settings page.”
In Firefox: “…Page not cached by WP Super Cache. Check your settings page.”
In CPanel: “…Cached page generated by WP-Super-Cache on …”
In W3C Markup Validation Service: “…Cached page generated by WP-Super-Cache on …”
In IsMyBlogWorking: “WP Super Cache is active….Page GZip….WP-Super-Cache age: 51543 sec”
In REDbot: “…Cached page generated by WP-Super-Cache on …”

I’ve checked my WP Super Cache settings in WP dashboard. All appears to be in order in terms of my settings. Why am I getting these different results in checking my source code and should I be worried?