Hi Mike,
Browser-based forms don't support attaching files (although there are rumors that this may be added in the near future).
You could use the InfoPath Web Part in SharePoint and have two web parts side-by-side that communicate and copy the link to the web page from the web page one into the InfoPath one. I think the chance of building something that worked well is low. It's a complex situation.
Another option would be to use a task pane. I know, you're thinking: browser based forms don't support task panes. And, that's true, but we have a toolkit that let's you extend the browser based form to use a taskpane. Your taskpane can then navigate to a Web page and insert the link to it into the form. Not as complex as the web part idea, but still not simple.
My two sense