How to go to WebPart maintenance Page in SharePoint

In SharePoint webpart maintenance is quiet common , but we only think about it when there is an error.If a page is not rendering properly then we start thinks about how to go to a webpart maintenance page. 

Append the query string ?contents=1 at the end of the page url and access the page which has some issues with webpart. It will take you to the web part maintenance page.