What are the legalities regarding using licensed fonts for webpages? It will be used for a for a commercial site. I do not want to get into trouble by using it without a license, (although I do hear a lot of complaints about the industry in general), but how severe are the penalties realistically?
There's no universal answer to this. You're also not really saying what you mean by "using" the fonts, though I'm going to guess you mean embedding. Even if not, the answer is pretty much the same:
You need to look at the license you agreed to, from the foundry that produced the font. Some of them have relatively liberal usage clauses dis/allowing use in certain media, some disallow embedding altogether, and some allow it as a sort of add-on to the base license.
If a site is caught using a font illegally the foundry will first send a DMCA take down notice.
In the United States:
Federal law provides severe civil and criminal penalties for the unauthorized reproduction, distribution, rental or digital transmission of copyrighted sound recordings. (Title 17, United States Code, Sections 501 and 506).
The license owner has every right to a lawsuit, whether they choose to pursue legal action or not is up to them.