http://toolbar.google.com/
& you need a google account so that you can carry your bookmarks in your account anywhere
Now restart your browser and on the google toolbar click on Bookmarks button
Now the last option would be Import Firefox bookmarks click on that,it will ask you to sign in to your google account once you do that it will show you the bookmarks added in your browser
Now you will see all the bookmarks that you have added to your browser and which you havent imported yet to google bookmarks,just select the bookmarks you want to import and click on the import button on top
You will see all your bookmarks in alphabetical order,now if you go anywhere in world and you need any important site or link that you added to your bookmarks,you just have to login to your google account to access your bookmarks
The same way you can do for internet explorer as well
Note: At this point of time google toolbar is available for firefox and IE only