How can I improve the functioning of this old iBook?

" I accidentally spilled Diet Coke on my MacBook (late 2009) and now it won't turn on."

Please don't attempt to turn it on. Here's my standard response for this horrible problem:

"Whenever a liquid spill occurs the first thing that has to happen is the laptop should be shut down immediately. All power must be removed as soon as possible. It is especially important that the battery be disconnected and removed.

All affected parts must be removed from the laptop. No attempt should be made to start/restart the computer.

Then all affected parts would be washed in deionized water and blown dry with compressed air. (In a water spill the deionized water is probably not as critical. Depends on the mineral content of the water.) and blown dry with compressed air.This is especially true of the large chips on the logic board. Water can wick under them and cause havoc.

The logic board should be placed in a drying/dehumidifing oven for at least two days. Longer depending on the spill.

The keyboard is a separate matter .."

So your original question:

That iBook will run 10.5.X but the RAM needs to be upgraded:

http://lowendmac.com/2005/14-1-42-ghz-ibook-g4-mid-2005/

There are other options for browsers to use:

http://lowendmac.com/2009/the-future-of-up-to-date-browsers-for-powerpc-macs/

For making your iBook 2005 run better, apart from adding some more memory —which I recommend you max to 1.5—you can:

1) Use TenFourFox as the browser. This is a browser aimed specifically at this age of Mac that runs Tiger, and it is kept up to date in alignment with Firefox. http://www.floodgap.com/software/tenfourfox/

2) Think of downloading iCab browser 4.9 http://www.icab.de/dl.php. This like TenFourFox is kept up to date, unlike TenFourFox it handles Flash videos. Unlike TenFourFox iCab will also cost you a one-off $20. I paid mine years ago and once you have a registration number the browser is available in different versions according to whether you are using an old PPC like the IBook on Tiger or eg an Intel Mac using Yosemite.

3) YouTube on this old Mac is sticky and jerky. Downloand Mr Gecko’s YouView designed, again, for old machines like this. You will get smooth YouTube performance. https://mrgeckosmedia.com/applications/info/YouView

4) Get some help for Flash, which will otherwise always give jerky video if it works at all. Download from http://scriptogr.am/nordkril/post/adobe-flash-11.5-for-powerpc

If you do all the above you will not get the performance of a state of the art present-issue Mac but will get a decent functioning computer well suited to the purposes you describe. Good luck with it.