Site slowed down due graphical content

If your Sharepoint site had slowed down considerably since you added several images to it, that's all because IE was checking every image to see if it had changed before displaying it.

A quick change to the IIS Application can improve the performance of the Site by simply adding a cache-control directive to the response headers...

cache-control: max-age=3600, no-check

Another way to do it is to use the BlobCache which can be configured in the web.config. It also adds the max-age to the response headers:

#BlobCache location="D:\blobCache" path="\.(gifjpgpngcssjs)$" maxSize="1" max-age="3600" enabled="true" /#