Service Level Agreement. When you sign up to host with someone, they (hopefully) sign a contract with you, part of which is a Service Level Agreement. In other words, we promise to maintain 98.5% uptime weekly. If we don't, we owe you a refund or, you kick our butt.
Plus some other legal mumbo jumbo.
See if they have a Terms and Conditions or User Agreement page or something. Call em and ask if they have an SLA. You might not, but wouldn't hurt to ask. Might mean some $$ back.