Always check every agent's/agency's guidelines -- some request query + 10 pgs, some query + X chapters, 5 pages, no pages at all... check and comply with their specific guidelines.
As to the website; it doesn't sound like you do have a platform; it sounds like you have a website, which is as meaningless in the grand scheme of things as the work-related writing to agents in general.
Agents are concerned with authors having platforms mostly in terms of non-fiction, when the authors are generally expected to be experts in their fields and, because many of the books are on specific topics (like, say, weight loss), it's beneficial to have a platform of followers or people familiar with your work built in, who would be interested, to help the book stand out from the crowd of other books on how to lose weight. With fiction, it's not the same. Aside from already-published authors, it's not so much a thing that there's an audience who will go 'oh, Bob wrote a book about a painter in 1930s France; I love his, uhm, ideas about France.'
In some cases of relevance, this is a thing -- which is, I'm guessing, why you noted you're not writing a novel that relates to legal themes. If Alan Dershowitz writes a legal thriller, there's some built-in audience, and he'd be wise to mention that little career thing he's got going in a query.
For most people writing fiction, not a thing unless it's specifically relevant in some way (you're pitching a novel about a high-end restaurant kitchen romance and run a blog about your adventures working in restaurant kitchens that has 300,000 followers. That's relevant).
Sorry about that.
