It looks like you're hosted on GoDaddy, which has recently upgraded the version of PHP they use. The errors are because something in your site (it could be a theme or plugin) isn't compatible with the new version.
There's an announcement about here, which includes some links about what to do next:
If you're locked out of your site, or don't remember how to get into your GoDaddy control panel, contact GoDaddy support, as suggested in the GD announcement.
You will have to upgrade WordPress and any plugins and themes you're using -- if your site is very old, you may have to update manually, using the instructions at this link:
After that, you'll be able to keep updated just by clicking a link -- it all gets much better!