Is there a "Recommended, Step by Step, Sequential order" to follow when installing Add-ons ?

I absolutely need these addons

  1. Column layout grid
  2. CSS Buttons
  3. Fast & Easy Checkout
  4. Sales Report
  5. Easy Populate
  6. Ultimate Seo



When I installed my last add-on (Ultimate Seo) installation, the /includes/functions/html_output.php was overwritten and now a blank page is showing up after hitting checkout ...

I removed "Ultimate Seo" and restored the original html_output.php file but the error is still there ...

Also does anyone know if Ultimate-SEO causes any conflict with any other addon, (especially CSS-Button addon) ? Because after installing Ultimate-SEO addon, my CSS Buttons disappeared.

I read somewhere that someone merged html_output.php in the CSS-Button addon with html_output.php in Ultimate-SEO addon. Does any one know how to merge these files ?