In Eclipse, can I remove the red error markers?

It's possible to tell Eclipse not to underline the text / show it in the vertical or overview ruler by unchecking all checkboxes in Window -> Preferences -> General -> Editors -> Text Editors -> Annotations -> Errors

As you only want to view the code, I'd recommend another editor like Notepad++, Sublime Text or (my personal favourite) vim/gvim. Eclipse is a little bit too 'heavy' for just viewing code.

If you are using the CDT plugin, which you probably are as you're using Eclipse for a C/C++ project:

• Window -> Preferences -> C/C++ -> Code Analysis.
• Disable Potential Programming Problems and Syntax and Semantic Errors.