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Internet Explorer 9 displays 2 lines of your most visited pages on the home page about:tabs by default, each line containing 5 thumbnails. However, if you want, you can customize IE9 to display more lines with a simple registry adjustment.
Open regedit and navigate to next button :
Right-click in space and create a new DWORD and name it NumRows. Give it a value 3.
Restart Internet Explorer 9.
You now see 3 lines.
You can specify any value between 2 and 5, the default value being 2.
Source : MSDN Blogs.
To edit this register, you must save the history. If you enabled Clear browsing history on exit, the registry entry for NewTabPage is deleted on exit from IE9 and you must recreate it each time you load IE9.