While regular advertisements are the most common form that you encounter on the Internet, for instance as banners on a website like this one, you may also encounter other forms of advertisement that are not quite as common, but often more distracting or annoying than the first kind.
A fairly new type are so called picture overlay ads that are offered by companies such as AdMedia and its overlay ads, GumGum or Linear Publishing to name a few companies. The ads are displayed on top of images on websites, usually in the lower half of the image.
They do take a quarter of a fifth of the image space effectively preventing the user from looking at the image in its complete form.
Count down pages are another form of advertisement, usually implemented by image or file hosting websites. They are intermediary pages that are displayed to the user for some time before the actual page with the requested contents are displayed in the browser.
They too can be highly annoying as you are forced to wait before you can continue whenever you want to download or view files that are hosted by these services. Sometimes, links are subject to this as well. They are popular on forums and other file sharing sites on the Internet, as part of the revenue from those ads goes directly to the user who created the doorway page in first place. Adfly alone for instance tracks millions of link clicks per day.
The userscript NoPicAds provides you with three different features. It blocks popular overlay image ads so that you can view the image in all its glory without ads attached to it. It also takes care of select count down pages by bypassing the directly so that you are taken to the countdown immediately without wait time. Last but not least, it is also preventing some pop up windows from being spawned in the web browser.
You find the list of supported websites listed on the userscript's page. Included are popular services such as adf.ly, linkbucks, reklama, imgonion, adcrun, abload, imgchili or urlcash to name a few. If you are looking for a solution for a particular service that you encounter over and over again, check out the list there to see if it is covered by it.
I have tested the userscript in Firefox with Greasemonkey, and in Google Chrome, and it worked in both web browsers without issues.
Note that other extensions may also block these types of ads. NoScript for instance takes care of image overlay ads by its own.
If you encounter image overlay ads or count down pages regularly, you may want to give this a try to speed things up for you and remove contents from websites that block your access to the real content that you are interested in.