You can create folders and use keyword tags to categorize your bookmarks.

When you've created folders, you can:

• Select a bookmark in your list and drag and drop it into a folder.
• Select the checkbox next to each bookmark you want to change and click the Move button on the action bar to move those bookmarks to a selected folder.

When you've tagged a bookmark, you can:

• Re-find it quickly by searching your bookmarks for that tag.
• View all the bookmarks saved with that tag by clicking (Use Tags) in bookmarks.yahoo.com.
• Add or delete tags by selecting the checkbox next to each bookmark you want to change and select Edit Tags in the action bar.