Signing up for Google Adwords and Microsoft Adcenter with a CREDIT?

I have a credit from my web host, but these sites want me to put in my credit card number. DOES THAT MEAN THAT IF THE $25 STARTING BALANCE RUNS OUT, THAT I CAN GO INTO THE NEGATIVE? Will it keep charging me?

oh yeah, you need to be really careful when running ads campaigns. i would recommend using an adward verification card instead of using your own credit card, it is way safer.
if you need any recommendation on where to find an adward verification card, just let me know, i know some cheap trusted ones

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