From Error, It seems that there is some issue with the component you have added.
Remove all the component you have added using page design or change the page design to Default one. And if page loads for you in experience editor with Default page design then there must be some issue with you component configuration.
Your error is locating the Main placeholder. If you have used partial design for main container then remove the that specific partial design and try to view the page.
It should work fine, if you haven't faced any issue during installation of SXA and site creation.