Stack Exchange network consists of 176 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.
Clicking on the StackExchange box in the top-left opens a transparent (no background?) box that covers most of the page in overlapping text. Opening this box on other sites (like Stack Overflow) opens a solid box, about 300 pixels on a side.
This has been fixed.
Thanks for reporting it.