We are using version 2012.Q3 of Telerik, for the RadGrid control.

Once we updated to VS 2013 Update 2, we experienced a rendering problem on our development machines for all RadGrids on our site.

Upon further review we found out that this was due to the Browser Link feature in VS 2013. Browser Link appears to inject code between the development environment and the web server(s).

We were able to fix this upon finding an article pointing us towards the Browser Link feature. However it did take quite a while to figure out the issue, so we wanted to pass this along so that you could create a Knowledge Base article about this so that others can find the solution more easily and quickly.

Resolution:
Add the following item to the AppSettings section of the Web.config
<add key="vs:EnableBrowserLink" value="false" />

References:
http://weblogs.asp.net/imranbaloch/archive/2013/10/23/messy-html-and-js-errors-when-you-install-visual-studio-2013.aspx

http://stackoverflow.com/questions/19513631/radgrid-rendering-differently-in-different-machine-of-100-same-application-when

http://www.asp.net/visual-studio/overview/2013/using-browser-link 
(what is Browser Link)