Black Diamonds/Question Marks

I am on a 2011 MacBook Pro, OS 10.9.4. After changing from a DSL modem to AT&T U-verse, I am seeing screens with text blocked by black diamonds with question marks in the middle. The screens are then replaced (automatically) by legible screens, but I'm not sure it's transmitting the same data. What are these black diamonds and should I be worried?

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Then provide more details about your problems.

Post has been edited for clarification.

In what application are you seeing these artifacts? If a web page, then that means that you are visiting a site that is using a font that you don't have on your system and thus getting the blocks and question marks and possibly other characters. But that wouldn't get fixed with a refresh or update, it would just stay that way..

So a little more context on WHERE you are seeing these things would help narrow things down..

Thanks for your reply. There doesn't seem to be a pattern. Sometimes it's when I click on a link in Yahoo and sometimes it's when I open my primary email account, but not every time for either one. I'll pay attention and see if I can figure out if there's a common denominator for when it happens.

As Raz0rEdge said, it's most likely in your browser and it is the result of a slow web site that tells your browser "there is a picture here, just a second and I'll get it" and then is slow about getting it and sending it. The browser shows the icon for missing data until the website provides it. If that is it, then it's either a slow internet connection or a slow website on the other end.

Thanks for your reply. Sounds right. Now I have to figure out what to do about it.
After changing providers from AT&T Yahoo DSL to AT&T U-verse, I am getting text that looks like this after I click on some Yahoo links, taking me from the main site. This is from

https://gma.yahoo.com/house-haunted...thon-121722875--abc-news-topstories.html?vp=1

Usually it is immediately replaced by legible text, but not this time. It's not over the whole screen, but just on a sidebar.

� �XYs�6 ~ׯ`�P�3"�ç 9#'M�i����n�� HBL ��8��݅x鰛��i�z�췋� ��n=eb� 6$4�bn����Ag������'��>q��j=$�, f=�v�H�0jh�q'9��Tnb�<�CbX��I*L�89m�Z |ֿ�u���=c�w�Ϻ�- iq�� !�!I��Xת�ǝ ~�F25����E��lŘ��ȌS<

This is only part of the sidebar.

That website looks fine to me. I wonder, have you installed anything to "clean" or "speed up" your Mac? It looks like you are missing some fonts.

Thanks, Jake. Are you suggesting that this could be caused by installing "speed-up" software or that I should consider installing some? I haven't installed anything new. I have a call in to AT&T and one to my primary e-mail provider techs, but so far haven't heard anything.

Some of the products sold to "clean" and "Speed up" Macs do a very poor job, even to the point of being counter-productive. The only clean up product you'll find recommended here is Titanium's Onyx, which is free and very good at what it does. In general OSX maintains itself without any third part stuff. There is a product that advertises it removes "unnecessary" fonts, but which has been known to remove fonts that are actually needed for the system to function properly. So, NO, I am not recommending any third-party maintenance products, other that the aforementioned Onyx.

Thanks! I'm still waiting for response from AT&T and primary email techs. I suspect that AT&T might have gotten creative with installation and dropped some fonts. Your responses give me some guidance on what to ask/tell them!