Here are some trustworthy and reliable websites which examine the use of weapons during WWI.
BBC World War I - technology, communication and weapons
This is an interactive website from the world renowned BBC service. Click here to visit this site.
The British Library - Weapons of WWI
There are many resources, including many primary sources, on WWI on The British Library website. This page focuses on the weapons of the war, including trench warfare, tanks and gas warfare.
BBC Bitesize - technology and weapons
Here's another site from the BBC which provides an overview of weaponry in WWI. Click here to visit this site.