You may have noticed the new Google search interface, which features a new left-hand navigation (left sidebar) and a modified Google logo which looks pretty cool. The new side panel highlights the most relevant search tools and refinements for your query, making it easier to find exactly what you’re looking for.

However, most users may find the new sidebar integrated to left of Google search results not useful and pretty annoying. There’s an easy way to hide the left-hand navigation pane/sidebar in Chrome and Firefox browser.
To Hide Google sidebar in Chrome, install the extension ‘Hide Google Options’. It’ll remove the persistent sidebar and also ensures the Options pane remains a choice for users. You can click its icon to alternately show or hide the options shown in the left-hand pane of Google search results. (Supports worldwide google domains)

To Disable Google sidebar in Firefox, install the add-on hide google option. You can easily enable/disable it anytime from status Bar in just a single click. Currently removes the sidebar only from search results.
Firefox users can instead install google fix user script (using grease-monkey add-on) which removes the left sidebar and bottom search bar from all regions of google search results, providing the Old Google interface.
Internet Explorer & Opera users can use this direct link to get back the old Google user interface. Bookmark: