As much as I like themes to personalize my Nokia devices they are also a cause for the vast majority of all questions I see in this blog.

"I have problems installing themes please help me" or "I get a "certificate error" message when trying to install a theme what do I do" or "I get an "certificate expired" error message when installing a theme please help"

Although this have been covered extensively in the past I guess it is still an issue.

If you try to install a theme and see the above error message "Certificate Error. Contact the application supplier" You are trying to installed an application that is not Symbian signed.

The solution is easy. Simply switch the setting in the Application Manager from "Signed only" to accept all - "Software Installation: All". You can find the application manager in the tools folder, then click on "Option" to bring up "Settings".

Another common issue is the "Expired Certificate" error. The certificate that the theme developer used may have expired. However, there is an even easier fix for this issue.

Simply set the date on your device back from 3 - 16 months and then install the theme. After you successfully installed the theme don't forget to set the time correctly on your device.

If none of those option works try to sign the application/theme on Symbian Signed:

With that being said I am now off to trawl the internet for some new great themes. If you have any themes to share with us please.