3 answers
Try using the Developer Console in Chrome. Hit Ctrl+Shift+I when you're looking at your Salesforce org. Then press Ctrl+Shift M to switch it to mobile view. In the address bar, erase everything after salesforce.com/ and replace it with one/one.app. Your url should look something like "https://(instance).salesforce.com/one/one.app". It should load the Salesforce1 mobile view. I've attached a screenshot of what mine looks like.
Unfortunately I don't know how to remove the sidebar with all the Javascript errors completely, but you can resize it to make it as small as possible. Hope this helps. I use this all the time for testing and demoing Salesforce1 functionality on my PC.
