I agree in principle with both chris and ron, however as I am not solo, but working in a design studio I'm kind of forced to utilise wireframes and mockups.
...so I get from the designers a pdf wireframe of the website structure and a basic webtree to start from. Before it's even got to this point ideally we've discussed the information architecture, the content layout and objectives. However more often than not this isn't the case and I end up with a lot of "lorum ipsum" frustratingly.
in essence this waters down the wireframe to a pointless exercise, as from this point forward the design would dictate the content, and not the other way around - as it should be, and it merely becomes a sketch from which to work from. I'd usually print it out and peruse it on occasions.
However, after I've been delivered a wireframe, I go to work creating the structure of the site, whilst it's design is being done. We work together on the design, I demonstrate to them how the structure will perform at different viewports and they adjust the design accordingly.
They then give me an in-design mockup, i take what assets i need and style it up. once that's done we review the site across mobiles, devices, computers, platforms and browsers - referring to the design. there's usually a few red flags and arguments at this point, still useability should always trump over design.
spit and polish. appease the designers, than compress the hell out of it, because it's probably going to need it.
it also depends on the size and scope of the project. a well thought out wireframe for a comprehensive site is actually very handy...