You should absolutely ask about it. Mention that you saw on the website that the company provides relocation assistance, and ask what the details are and if they would provide you with the assistance.
When I received the offer for my current position, no mention was made of relocation assistance (and none of my coworkers were aware of it either!). I found out somewhere (most likely the web site or some benefits flyer I got at the interview or as part of an informational packet), and asked the HR person about it. The response I got was along the lines of "it looks like you qualify (distance), let's see if we can get the money approved", followed a day or two later by "here's your relocation assistance".
The actual relocation was contracted out to a relocation company, so if you're looking for a general guideline of what to expect, I'd suggest searching the internet for such companies to see what they offer (although the most accurate/informative way to find out is from the company making the offer).
Things that I recall were available through my relocation package included:
- temporary housing near the employment location (choice between hotel or furnished apartment)
- access to a realtor (to help find a permanent place)
- a chunk of spending cash (not sure how common this would actually be)
- covering/assisting with costs associated with selling a house or breaking a lease
- shipping of household items.
I didn't have need of all of them, but it was nice to have the option open.
One potential thing you may have to consider: some companies may just pay the cost for this upfront, but it's also likely that since they are making a bigger initial investment in you, they'll require that you pay back some (or all) of their costs related to relocation if you leave the company within a certain time frame (6 months, 1 year, or similar, probably depending on their costs).