Search the existing threads before posting anything
Try disabling your other extensions first to see if they don't interfere, or if it seems that Imagus is interfering with page functionality, then disable the extension and see if the problem is persistent
State your browser and its version, and use the most recent version of the extension
Detail your problem (simply saying "doesn't work" is not helpful, be specific), preferably include reproducible steps, optionally a screen-shot/cast if the problem is visible or hard to describe
Always provide URLs where the problem occurs ("some or all thumbnails don't work on xyz" is not enough, point exactly to the broken ones), if the page requires authentication then mentioned that too
If you don't use default settings, then list the ones you changed

When requesting site-support

The URL of the page is required, and over what links/thumbnails on that page you want it to work

How to import a rule

Options / Sieve / import button (↓) / copy-paste the rule that you were given into the text-box and press the From text button / Save. If the rule already exists, you have to tick the "Replace existing data" checkbox before saving.

How to create a rule

Adding your own rules can be done at Options / Sieve by clicking the + button, fill the input boxes and finally hit Save. To make rules you need to know at least Regular Expressions and HTML, and for more complicated situations you need JavaScript. A weak explanation about the parameters can be found here.