The forum is set to a standard desktop theme and can be difficult to view on a phone.
There are links in the top menu which present the content in boring text only formats.The forum stats report that all users currently use the forum default.You can change your theme to 1 of the 2 other themes in your profile.Both of the additional themes are more phone friendly - you can always change back so don't be afraid to tinker.
To change... go to
Profile - Look and Layout.