Using an UMPC you will often find that the browser uses a lot of the CPU power decreasing overall perfomance and hindering your multitasking. To improve browser speed there are some options. Here are two Mozilla addons to consider.

Flashblock

What is Flashblock?
It is a simple Firefox addon that stops flash videos and ads on websites thus saving a lot of CPU power.

Why use it?
If you have an older PC, a low spec laptop or use an UMPC, netbook or MID this simple program can really speed up your internet experience and your overall performance if you run a browser in the background.

What are the drawbacks?
You have another program running in the background so you need to check how it effects your performance. It will also sometimes block flash units you could be interested in.
It only works for Mozilla, Firefox, and Netscape browsers.

Where can I get it?
Get it here and read more about it before you download.

NoScript

What is NoScript?
NoScript is a simple addon that blocks java, javascript, flash and some plugin scripts from running in your browser.

Why use it?
Again, for lower spec pc's, laptops and all types of mini-pc's this script can speed up your internet browser and your overall performance. It also protects you from malicious scripts because they are blocked pre-emptively.

What are the drawbacks?
You have to manually allow or disallow scripts by adding them to your trusted sites or not. A lot of sites also use scripts for perfectly legit reasons so need to keep checking if you're not blocking a script you may want or need for viewing the site.
Only for Firefox, Flock, Seamonkey and other mozilla-based browsers.

Where can I get it?
Get it here and read more about it before you download.