Is it safe to use kubuntu-ppa

I have just take a look in the software sources and see there the kubuntu-ppa/backports.
When I use these I see a lot of updates. There is also a warming of all updates must installed.

Can someone tell what the best suggestion is?

i have twice the first one is kubuntu-ppa/backports and the second one is kubuntu-ppa/backports (sources ) , they are un-checked , i have checked the first one and i found alot of updates applications and system updates , some of them is not checked and there is a notification in muon update center says that there are some updates unchecked if i want to check all or not , i didn’t know what should i do then I have canceled it and unchecked both of kubuntu-ppa/backports and kubuntu-ppa/backports (sources) what is the use of those ?
by the way i cannot find any updates for firefox i am still on version 21 and i don’t know what to do

I have the same ppa here.
I have just take a look here and I have also firefox 21. I don’t use firefox here. I use here thunderbird and have 17.0.8. I have take a look and see the same version on the site.

yes i have the same version of thunderbird , but for firefox there latest version is 23, i don’t know why i don’t receive any updates :-/.