Designed to Fit Your Visitors’ Screen
To view the screen resolution statistics of your site’s existing visitors, access your Google Analytics account.
Click “Standard Reporting”
Select “Browser & OS” from the “Technology” Menu along the left side-bar.
About half-way down the page, select “Resolution” from the “Primary Dimension” menu.
The result will be a report displaying data something like this.
If I were to re-design this site to be best viewed on a display 1024 pixels long and 768 pixels wide (or better) my design would match the display resolution of 42.4 % of my existing viewers.