What is the best bookmarking site for multiple computers and browsers that's NOT focused on social?

I'm not interested in social bookmarking. I have three computers, 3 different browsers on each one, and sometimes use the library computer. I want a free online bookmarking website that can handle imports from opera, google, firefox, chrome and google. Sometimes just importing an HTML file doesn't work on these sites. And synchronizing would be nice - or a fast way to add bookmarks that doesn't take forever. Operas is my main browser and I have well over 1000 bookmarks. Some sites don't work with Opera. Not sure why, but they don't. Any suggestions/experiences??? (And free version of transmute only overwrites bookmarks..can't merge except in paid version.)